Simultaneously the most infuriating and the most important line in the London Underground system, the Circle Line has been, and continues to be, the commuter's best tool for getting around the dark intricacies of Zone 1. As a result, if you can manage the Circle Line effectively, then you should be able to cope very well with the rest of the London Underground system.

Way back, when the first London Underground lines were introduced, it was proposed in 1863-4, that on the back of the success of what is now known as the Hammersmith and City line, there should be a 'circuit'. This would connect Paddington and Farringdon with the main-line (National Rail) stations of what is now the most southerly parts of Zone 1: Victoria, Charing Cross, Blackfriars and Cannon Street.

A further extension was proposed to include the stations Liverpool Street, Broad Street, and Fenchurch Street. Unfortunately, this proved to be awkward, as trains had to double-back at Aldgate, increasing costs and reducing passenger numbers at the time.

Another proposal at the time was put forward - that of extending the line westward to include South Kensington and extending it eastward to Tower Hill, pretty much giving the Circle Line its present form.

It could be said that this is where the problems began for the beleaguered Circle. Due to financial constraints and disagreements with rival companies, the Circle Line's circle completion was delayed until 1905. This was because, at the time, London Underground was not a publicly-owned company, but leased out to private contractors by Parliament1.

It has remained largely unchanged to this day.

The Circle Line is so busy due to its stations being in such close proximity with popular sights of London, main-line stations, and also to its corporate and financial centre; called The City. Just to give an idea of what there is to see, here is a full descriptive list of all the stations of the Line with which stations have National Rail (NR) links, and what places of interest are within walking distance of the station.

There is no real starting point for this Line as it is a circle. But for argument's sake, going clockwise from Embankment:

• Westminster - for the Houses of Parliament, Whitehall, the London Eye and the London Aquarium.

• St James' Park - for the Royal Park of the same name and Buckingham Palace.

• Victoria - NR

• South Kensington - for the Victoria and Albert Museum, the Natural History Museum, the Science Museum, Imperial College, the Royal College of Music and the Royal Albert Hall.

• Gloucester Road - for Esquires. Not a sight as such, but it does sell the best coffee in London. Their Café Mocha is highly recommended, especially with a 20% discount to Imperial College students. Also the legendary Sandwich Shop where you can order probably the best tuna and salad in a demi-baguette for £ 1.50 (at time of writing, of course).

• High Street Kensington - for all manner of shopping. It has a Gap store that opens until 10pm on Thursdays and a Benetton store which does something similar.

• Notting Hill Gate - for Portobello Market and the setting for the film Notting Hill.

• Queensway - for Kensington Gardens and Kensington Palace.

• Bayswater - for various restaurants.

• Paddington NR, for all aspects Paddington Bear, and St Mary's medical school, where Sir Alexander Fleming discovered penicillin's antibiotic aspects.

• Edgware Road - nearest Paddington Green, famous in the UK after being the subject of a docu-soap on the BBC.

• Baker Street - for Madame Tussaud's, The Planetarium, and all things Sherlock Holmes.

• Great Portland Street - for Regent's Park and London Zoo.

• Euston Square - not a NR station but near one; Euston, a short walk away.

• King's Cross/St Pancras - NR.

• Farringdon - NR.

• Barbican (formerly Aldersgate) - for the Barbican Centre, Charterhouse School, and historic Smithfield Meat Market

• Moorgate - NR, and a short walk to Bunhill Fields - final resting place of William Blake, John Bunyan and Daniel Defoe.

• Liverpool Street - NR.

• Aldgate - for The City, and Petticoat Lane Sunday market.

• Tower Hill - for the Tower of London and Tower Bridge.

• Monument - for the Monument to the Great Fire of London.

• Cannon Street - NR.

• Mansion House - for the Lord Mayor's Residence and also a short walk to St Paul's Cathedral.

• Blackfriars - NR.

• Temple - for the Temple, Somerset House and King's College.

• ...and back to Embankment - for the Ministry of Defence, Cleopatra's Needle, and Hungerford Bridge; for access to the arty South Bank.

Technically it is in fact a 'sub-surface' line, running not much deeper than the basement of surrounding buildings. It was built by the 'cut and cover' method, where a deep trench is dug and then covered over. Along some parts of the line the trench was left open, and the sky is plainly visible from some sections of the Circle Line as well as from a number of stations along its route. Compare this to the later 'deep level' tubes such as the Piccadilly and Northern Lines, which run much deeper and were dug using tunnelling machines.

It is not a stand-alone line. In fact, due to its building history it shares its route with the following lines (going clockwise):

• The Hammersmith and City Line from Paddington to Liverpool Street Station.

• The Metropolitan Line from Baker Street to Aldgate.

• The Upminster/Ealing Broadway/Wimbeldon/Richmond District Line Service from Tower Hill to Gloucester Road.

• The Edgware Road District Line Service from Earl's Court to Edgware Road.

• The Kensington (Olympia) District Line Service, via Earl's Court to Edgware Road.

Even with no real termini, its depots are in fact the same as those for the Hammersmith and City Line. This is due to the fact that when it was first built the Circle Line was virtually running the same route. Hence now, the Circle Line, operationally, is merely an extension of the Hammersmith and City Line. As a result, trains for the Circle Line come from Hammersmith or Neasden and start at Paddington or Baker Street respectively, and go around the circle once. Theoretically, the drivers should change here too.

Where do other Tube trains go to die? There is a Tube train 'graveyard' which can be seen from a Piccadilly Line train on approach to, and leaving Acton Town Station. This is where trains wait for their fate to be decided. Not all die, of course - some are recycled as Circle Line Tubes. Regular travellers may find themselves on a defunct Hammersmith and City Line train. It's good to know that they can still run even after taking a battering on the deep lines, and be reincarnated into a new service by a new lick of paint.

There are several reasons that all Tube trains face delays. The problem is that when a Circle Line Train faces these challenges, due to the stations being in places used most often by lots of commuters and tourists, any slight delay is hence multiplied. Here is a list of common reasons for delays:

Now this is a very serious reason, as there may be a bomb in the 'package' left on the station. But then there may be not. It is more likely that a passenger has forgotten their baggage. This is why all passengers of the Tube should take all belongings with them to prevent unnecessary alerts. However for obvious security reasons, London Underground treat all suspect packages as being real live bombs.

Obvious and rare, but they also have to close off other stations in case there are more devices found.

Some terrorist groups tend to give a coded warning to the police, London Underground or a media network. Either way, the threat is taken seriously and the station is closed quickly.

If there is a track defect, signal failure or not enough drivers, then London Underground staff tend to react with safety at the forefront of their minds. Often speed restrictions will be enforced if a track defect is reported; if a train is defective while en route, then it will be immediately taken out of service. All tend to lead to a backlog of trains. This is due to the circular nature of the line.

Because the line runs so close to the surface, delays can occur when heavy rain causes flooding on the streets above. Often the track itself is flooded or the water has caused problems with the power supply. Again, this leads to a backlog of trains.

As the Tube runs off electricity, if there were to be a power failure, not enough trains may be on the Line to cope with passenger numbers; again, causing another backlog.

Again, due to the sub-surface nature of the Line. This used to be thought of as a pathetic excuse, often used by the National Rail operators to explain delays in Autumn, however there is a very serious reason for this. Leaves fall on the tracks and consequently get crushed by the train. More leaves fall and get crushed. Eventually, this makes a very slippery pulp which causes the train to slide along the rail on braking. The pulp also takes time to remove and requires a special machine to do so.

The Tube is an old system; some of the structures are in fact over 100 years old. An example of this is the southern entrance to High St Kensington station which has had work done to strengthen 100-year-old arches, which had failed safety checks. There were no District Line Earl's Court to Edgware Road Services, and hence people who would normally take this Line where told to change at Gloucester Road for the Circle Line. This added to passenger numbers and hence the time people would take to get on and off the train. All these little delays eventually created a backlog of trains.

In this, the driver has to stop the train, give an announcement as to why, and check what is happening. If something serious is happening, then usually, the train will remain at the platform for a very long time, while the situation is resolved. This causes a very long queue behind this train, and hence, more delays.

This will often occur in winter, when most of the general public have coughs and colds. However, sometimes it will occur because a certain rail union is on strike, or if London Underground haven't employed enough drivers.

Occasionally, most of the trains will develop a fault. Again, they will be taken out of service. This tends to leave the service with not enough trains for the number of passengers waiting, again, leading to a backlog.

At the time of writing, this is happening more and more with the run up to the Public-Private Partnership, which rail unions oppose. There are no drivers and no staff at all. In this case, it is not just the Circle Line, but the whole Tube network which is shut down.

This is a very common reason on all the Tube Lines. At certain times of day, when the trains are very busy, the carriages are so full that many people struggle to stand clear of the doors. The train will not move until the doors have enough room to close. However, some people fail to heed this warning, even when the carriage is not full. This does not provide any amusement for the train driver, or your fellow passengers, as now they will be holding up the entire network, creating yet another backlog of trains.

The Tube map is poor in a few respects, one being that it gives no indication of the distance involved in changing Lines. On the Circle Line, there are several occasions at some stations, particularly at the following, where the walking distance is especially distorted:

• Hammersmith and City Line to the Circle Line at Paddington - the Lines are at opposite ends of the station. However, this is only the beginning; you are not even at the station concourse and there is far more walking distance to be covered. In Tube maps, the Lines are all interlinked in what is known as the Paddington Triangle.

• Bakerloo Line at Baker Street - this is an escalator job, due to the Circle Line being sub-surface, and the Bakerloo being deep.

• Piccadilly and Northern Lines at King's Cross - this either involves a walk through some very long tunnels, or crossing several roads overground, depending on which signs you follow.

• Bank to Monument - Bank is not on the Circle Line, but on the tube map, it seems to be connected. It is, but it may be best to walk overground to it, rather than going via a long tunnel.

• Jubilee Line at Westminster - again, this involves going up several escalators, or, walking it all.

• Central Line at Notting Hill Gate - another escalator job.

Unlike other London Underground Lines, on the Circle Line there is no obvious terminus. However, to keep in line with the rest of the tube network, the Circle Line runs Westbound and Eastbound. If you look at a Tube Map, you will find that this is not true. As a train reaches Liverpool Street running clockwise, it seems to run Southbound.

Despite that being very illogical, there is a reason behind this. The Circle Line stations share its platforms with older Lines, eg the Metropolitan Line, which have quite obvious Westbound and Eastbound direction.

So how do you know which platform to go to? There are three ways of doing this. For this, you need a tube map. Find your starting place, and where you want to get to. Also look at the nearest NR station on the map.

• Check the boards before getting on the platform - ignoring the West/Eastbound text, see if your destination is on the board. If it is, then that is the right platform.

• Guess which platform is the right one and then look on the Electronic sign or the Light Box with arrows on it - these should then read: 'Circle Line via XXXXXXXX', the 'X's representing any one of the stations in between where you are and your destination.

  For example, if you are at High Street Kensington and want to go to Embankment, the sign should read 'Circle Line via Victoria'. If it doesn't have any of the stations in between where you are and where you want to get to, then you need to use the next step in conjunction.

• Follow the instructions above, up to looking at the Electronic sign - if the sign doesn't read any of the stations in-between, but the correct NR station, then you are on the right platform.

  For example, you are at Paddington, and want to go to Baker Street. The sign should read, 'Circle Line via King's Cross/St. Pancras'. If it doesn't, then you are definitely on the wrong platform.

Alternatively, it may be simpler to ask one of the London Underground staff. These people are easily recognised by their blue uniforms, and are incredibly helpful in providing accurate information.

On arrival at the station's platform, you will find an electronic, over-head sign. '1 min' on the sign does not mean 'train will arrive within 1 min' but 'you will have to wait at least 1 min'. An accurate way of finding out how long you will have to wait for the next train is by asking one of the London Underground staff. However, remember that they are likely to be very busy, so it pays to be patient and courteous to them, especially if you want them to help you.

This always causes confusion due to the tracks being shared. So here are a few distinguishing features to help you get on the right train:

• District Line trains - these are either the rather boxy looking type, or the more modern tube type. Check the front of the train as they arrive for the destination. They usually go to Ealing Broadway, Richmond, Wimbledon, Edgware Road or Upminster. With the exception of the Upminster bound trains, the rest are very similar to the Circle Line trains. Check the front of the train to be sure.

• Metropolitan Line trains - these usually have brown/burgundy rails, and have seats facing or opposing the direction of travel.

• Hammersmith and City Line trains - these have pink rails. Also check the front of the train for the destination. They are usually for Hammersmith or Barking.

• Circle Line trains - these have no destination on the front of the train; instead, they should read 'Circle Line'. They also have yellow rails.

Circle Line tubes are notoriously late - occasionally so late that the next train will not register on the board. Expect to wait at least 20 mins for a Circle Line train. It has been known for people to be waiting 45 mins for a Circle Line train, though those are the die-hard determined.

When a train finally arrives, it is likely to be packed. Despite this, you may not see another one. So hold in your stomach, take a deep breath and squish your way in, remembering to let passengers off first.

Do not expect to breathe comfortably while on the train. The carriage is full of noxious odours, and it will get very hot in there, especially in summer. Drink plenty of water beforehand. This is not a joke. Fainting has been documented on this Line, and a bottle of water plus a newspaper to fan yourself with can reduce your chances of this happening.

The train will move, albeit very slowly. It will also take the opportunity to stop at seemingly random moments for no apparent reason. Train drivers are now getting the hang of making announcements, and the reason behind the stoppages is to 'regulate the service' ie, to prevent three Circle Line trains turning up when you only want one. However, there is very little chance of this happening.

This all culminates in you getting to your destination, sweaty, hot, and very late. So why bother using this at all? Here are a few examples of alternative routes for some common trips.

• Tube Route 1 - take the first Westbound District Line train to Earl's Court. Cross over the platform to wait for an Edgware Road District Line train.

• Tube Route 2 - take the Piccadilly Line to Piccadilly Circus. Then change for a Northbound Bakerloo Line train. This is best used for those with not much to carry.

• Walk - it's much nicer, healthier, although not advised on your own. This involves walking through Hyde Park, from Alexandra Gate at Exhibition Road, past the Serpentine Gallery, over the Serpentine itself and exiting through Victoria Gate, at the north end of the park.

  Turn left to walk down Bayswater Road. Then take the third right down Westborne Street. Continue walking straight ahead, up Westborne Terrace, and Paddington Station should be there in front of you.

Despite this being only one stop, you'll be wanting to change here from a Westbound Piccadilly Line train or a District Line train. There are two pleasant alternatives, walking it or bussing it.

• Bussing it - this requires you to catch a No. 49 bus running toward Shepherd's Bush, which goes all the way to High Street Kensington.

• Walking it - this runs along the same route as the bus. Turn left out of the station, where you should see a crossroads2, and a road in front of you. Walk down this road as far as you can humanly do so. The aim is to meet another main road (ie Kensington Road), and see Hyde Park. Turn left, walk on, and you're on High Street Kensington.

• For the Tube die-hards - go to Earl's Court on a District line train and change to an Edgware Road train. This is not recommended.

The main theme is that walking is visually nicer. If you are a tourist you get to see a lot more of London this way, and it's also quicker.

But it's not all bad. The Circle line can be a lot of fun too.

As it takes so long to get wherever you want to go, it is the best place to have deep meaningful conversations with colleagues and acquaintances. Meetings can also be had here, even in the less than sexy surroundings of a Tube train. Around Westminster, the trains become packed with politicians released from Parliament. If you listen carefully, you may even hear their policies discussed honestly pre-spin, or dark plans for leadership being made. More likely is that you'll meet a junior minister or civil servant.

There are many pub crawls to be had in and around London, one being the Monopoly Board pub crawl; a difficult and time-consuming exercise, as there is no obvious public transport route. However, it has a much easier sibling, The Circle Line Pub Crawl.

Aided by being transport-friendly, it is also a familiar crawl to be popularised by students on their RAG Week3. The aim is simple. Get round the Circle line starting at South Kensington or any other station, and return, while collecting lots of money from Tube passengers and pub patrons. Alternatively you could forgo the charitable latter and treat it as a normal, basic pub crawl. Here are the rules:

• There is at least one pint of beer/lager or one shot of spirits to be had at a pub near each station.

• When on the Tube, you cannot sit down or hold on to the rails for support. Thus, one 'surfs' the Tube. This gets progressively more difficult as you get more inebriated.

• Return as quickly as possible or before the Tube shuts (this is about 12:30 am) with the aim of getting as far around the Circle as you possibly can.

Well, as the Circle Line goes, it is probably the most ridiculed and under-funded of all the Lines in the Tube network, so there are no surprises to the delays and cancellations. The best advice is that if you find a Circle Line train waiting on the platform; take it to wherever you need to go. It may be hot, smelly and sweaty, but it is the only Line in which you'll feel a sense of achievement on exit.