Naismith's Rule - 12 minutes per km plus 10 minute per 100m ascent.

This means travelling at 5km/h on the level, which I think is probably a bit optimistic. I'd say 4km/h which means 15 minutes per km.

Carlingford is a beautiful town on the southern shores of Carlingford Lough, a long narrow inlet. South of the town are the Cooley Mountains and across the lough are the Mourne Mountains. Carlingford has a big harbour with plenty of parking, a tourist information office (in the Summer), a recommended cafe (Ruby Ellen's Tearooms) and a Michelin-listed restaurant (The Bay Tree).

There are a number of walks in the area:

• The Carlingford - Omeath Greenway. This is a very flat walk along the banks of the lough along the path of an old railway. It's suitable for walking or cycling, but since it is only a few kilometres, it's probably not worth cycling it.

• 1a The Commons Loop - Green Arrows - Grade Easy - 4km - ascent 250m - 1h 15m

• 1b Slieve Foye Loop - Blue Arrows - Grade Hard - 9km - ascent 270m - 2h 30m

• 1c The Barnavave Loop - Red Arrows - Grade Hard - 14km - ascent 400m - 4h 30m

• The Rooskey Loop - starting from John Long's pub, Grange - Grade Moderate - 7km - ascent 150m - 2h 30m

• The Molly Loop - starting from John Long's pub - Grade Easy - 4km - ascent 120m - 1h 30m

• Carlingford Long Walk (my invention) - Grade Medium - 19.8km - ascent 350m - 5h

Access points along the Greenway? The website claims there are five, but doesn't say anything about where they are. I contacted the Carlingford Tourism, but they didn't reply. Only seems to be one useful one, at the pier.

The Barnavave Loop looks hard. Originally I thought it went the other direction which made it even harder. As it is, going anticlockwise, the climb is more gentle, and you have the option of chickening out and avoiding the peak.

Carlingford Long Loop

My Carlingford Long Loop is a combination of the Greenway, the Slieve Foy Loop and the Rooskey Loop. It's been tailored to be around the 20km mark, and has a pub at the 16km point to provide a break.

1. Starting at the Tourist Information Office, head north and turn right towards the pier. (There are public toilets just after the Civil Defence building.) Just before the Civil Defence building, climb up the steps to the castle, cross the bridge over the main road. Continue north, rejoining the main road briefly, then turn right down towards Carlingford Marina. At the Marina, take the Greenway path (which is to the left of the car park).

2. Follow the Greenway for 3.7km until Greer's Quay. Head inland, turn right onto the major road (Carlingford to Omeath) and proceed for 130m.

3. Turn left and follow the Táin Way up the hill. Continue to follow the Táin Way. It stops climbing and turns left. Then it is fairly level for about 2km. The road turns through 180 degrees back on itself to the right, then ends at a small car park. Just before the car park, on the left (uphill) side is the Slieve Foy Loop walk.

4. Follow the Slieve Foy Loop walk (blue arrows), heading uphill again. The route then turns left to follow the top of the Slieve Foye Forest along the side of the mountain. When the path reaches the end of the forest it continues along the side of the mountain for about 200m and reaches the Táin Way again.

5. Turn left onto the combined Slieve Foy Loop and Tain Way, following it down the mountain until you reach a road.

6. At this point, you can skip most of the southern part of the route, shortening the total to 13.2km: turn left onto the road and keep going downward until you come to a T-junction with Rooskey Road. Turn left, then left onto Dundalk Road and finish the walk as in step 12.

7. If you don't want to cut the walk short, turn right onto the road and proceed for 1.7km. This is a very small road with only the occasional car and with grass growing down the middle in some places. There are fine views out over the lough. You'll pass a small turn to the left and then three houses in a row on the left. Facing the third house is a gravel area on the right. At the end of this, take the lane which bends slightly to the right.

8. After 300m, turn sharp right onto the Rooskey Loop. You're now going backwards around the Rooskey Loop, so the purple arrows will be pointing in the wrong direction. After 500m you reach a bigger road (Rooskey Road).

9. Turn right onto Rooskey Road, then almost immediately turn right again off the road onto Billy's Lane. After 800m, turn left onto a small road, cross the major R173 road and then reach the crossroads at the village of Grange. Here you can take a break in John Long's Pub, it it's open.

10. Continue on the Rooskey Loop (heading east from the crossroads) on Skeehan's Lane. After 1km, you cross a road and go straight on onto an unsurfaced path just to the left of the driveway of a house.

11. Continue on the footpath, which is known as Forty's Lane. After another 1.5km, the route comes back out onto Rooskey Road. Turn right onto the road, leaving the Rooskey Loop. The ruins of Rooskey Priory are now on your left but there appears to be almost nothing to see.

12. Follow the road all the way back into Carlingford, turning left onto Dundalk Road and turning right at the the Oystercather Lodge onto Market Street. This brings you back down to the Tourist Office and the end of the walk.