It described a series of interconnecting canals which could be navigated, usually in a week or two, without having to cover any section twice, and has subsequently been applied to several other such routes.

The term was coined by enthusiasts as an adjunct to the South Pennine Ring, devised as a marketing tool by British Waterways.

[2][3] The Leigh Branch of the Leeds and Liverpool Canal runs for 7.3 miles (11.7 km), mostly through a landscape which has been severely affected by mining.

For most of its length, the canal is on top of an embankment, which has been repeatedly built up with mining waste as the land on either side has been affected by subsidence.

The pound is level for 9 miles (14 km), and the next locks start where the Lancaster Canal Walton Summit Branch turned to the north.

As the canal continues to the east, there is a mix of industrial development, green fields and wild moorlands.

It was the scene of a famous incident in 1912 when a cow fell into the canal, and proceeded to swim through to Foulridge, where it was given alcohol to revive it.

Several more locks, grouped in twos and threes, with some single ones, continue to lower the level until Leeds is reached, where River Lock connects the canal to the River Aire and the Aire and Calder Navigation.

Between Wigan junction and Leeds, the canal covers 92 miles (148 km) and there are 85 locks, 41 to the west of the summit and 44 to the east.

[9] At Knostrop, the navigation enters its own channel, with the river to the north, and it remains separate for 7 miles (11 km) until the two rejoin at Lemonroyd.

At Stanley Ferry, two aqueducts carry the navigation over the Calder, the newer one of which was opened in 1981 to prevent damage to the older one by large barges.

At Battyeford, there is a large sewage treatment works, and the navigation turns to the left to pass under a railway bridge.

A compromise was reached with the introduction of West Riding narrowboats, which were short enough to work through both systems.

The journey through it takes around three hours, and convoys of up to four boats can pass in each direction on days when the tunnel is operational.

To the south of Mossley is Scout Tunnel, just 205 yards (187 m) long, and a little further on, the canal is straddled by an electricity pylon.

The canal is 6.7 miles (10.8 km) long, has 18 locks, and passes through a dense urban landscape.

[19][20] The final section of the Outer Pennine Ring follows the lower part of the Rochdale Canal.

The North Pennine Ring, which followed the Calder and Hebble Navigation above Cooper Bridge, continues along the main line of the Rochdale Canal above Ducie Street Junction and rejoins the Outer Pennine Ring at this point.

There are nine locks on this 1.2-mile (1.9 km) stretch, which passes through urban Manchester, to arrive at Castlefield Junction on the Bridgewater Canal, completing the ring.