The finest pint of beer available anywhere in the world is served in the pub The Diggers in Edinburgh. That isn't just a personal opinion; CamRA1 think so too. The entry for The Diggers in their Real Ale Guide reads simply 'Mecca'.
Beer brewed in Scotland mainly comes in two distinct varieties2: 'Special', also known as 'Seventy Shilling', because that's how much tax was paid on a barrel, many years ago; and 'Heavy', or 'Eighty Shilling'.
Heavy is darker in colour, stronger, and more full-bodied than Special. Most Scottish breweries produce their own, but The Diggers sells McEwan's Heavy. So, indeed, do many other pubs in Edinburgh and throughout Scotland, yet nowhere does it taste as wonderful as it does at The Diggers: smooth and creamy, once tasted never forgotten.
The proper name of The Diggers is The Athletic Arms. Its nickname comes from its proximity to a cemetery, whose gravediggers would visit the pub at the end of the working day to wash the dust from their throats. Its decor makes no concessions to modern taste: cracked linoleum, threadbare upholstered benches and wobbly tables. There is no juke-box and only a couple of ancient fruit machines. Apart from a few photographs of the Scotland football team, circa 19743, that's it. This is a pub where people go to drink, not to admire the surroundings. It's a place where Lawrence Llewellyn-Bowen4 would have a field-day, except that they'd throw him out as soon as he opened his mouth - unless it was to order a pint of Diggers' Heavy.
The Protocol of Ordering a Pint
Not that it's actually necessary to speak to order a pint. It's easy to spot those making their first visit: they'll come through the door, walk up to the bar and then place their order. Regulars come through the door, hold up a number of fingers representing the number of pints they want to buy and, by the time they reach the bar (a matter of only a few steps), the drinks will be waiting for them. Subsequent rounds are purchased by approaching the bar and telling the barman: 'Three5, please.' Note that the word 'Heavy' is never mentioned - it's assumed that's what you're ordering, because it invariably is. There are 16 beer taps in The Diggers: one for Guinness, one for lager, and the other 14 for Heavy. People drinking anything else tend to go somewhere else: legend has it that on busy nights anyone ordering lager will be politely directed to another pub 50 yards down the road.
A Personal Experience
The urban tale above may well be apocryphal, but this one is definitely true6. I know, because it happened to me. A group of us were in The Diggers at the beginning of a stag-night pub crawl. It was my round, so I did a quick headcount and said, half to myself, 'Right - eight pints'. One member of the crowd piped up: 'No, I'm on lager'. We tried in vain to explain to him that in The Diggers, you drink Diggers' Heavy and that's not negotiable. Eventually I went to the bar and placed the order. 'Seven please!' The barman started to turn away to pour the pints, so before he got out of earshot I added: '...and a pint of lager.'.
Instant silence. It was like a scene out of a Western movie when Clint Eastwood walks into a saloon: everyone in the pub was staring at me. 'It isn't for me!' I said and started drinking one of the pints of Heavy to make sure everybody understood that. The barman had only worked in the pub for about five years, so he had to ask another member of staff where the lager tap was, but eventually he poured a pint, looking at it with a mystified expression on his face as if wondering why it was a funny light golden colour. Meanwhile, I loaded the seven pints of Heavy onto a tray and took them back to our table, leaving the lager drinker to go up to the bar and collect his pint. Serves him right.
So what's the secret? Why doesn't McEwan's Heavy taste as good in any other pub? No-one knows7, but various theories have been advanced over the years. Some say that the manager pours a bottle of wine into every barrel, but this has been emphatically denied. The manager himself - now retired, sadly - puts it down to keeping the pipes meticulously clean, and maintaining the pub cellar at a temperature different from that recommended by the brewers, athough of course he won't let on what that actually is...
So don't worry about why it tastes so good - just accept it. And enjoy.