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.

This was originally considered to be the main line, as the canal was connected to a series of underground levels which ran into the coal mines at Worsley.

One feature was a huge aqueduct, 38 feet (12 m) above the River Irwell, which allowed sailing ships to pass beneath it.

It was demolished when the Manchester Ship Canal was built, and replaced by the famous Barton Swing Aqueduct.

[5] The length of this section is 13.6 miles (21.9 km),[3] and it is operated by the Manchester Ship Canal, although there is no additional charge for boats with a current British Waterways licence for the first seven days of use.

It now sits on top of an embankment, made for waste from the pit tips, and the locks have been moved to Poolstock, just before the junction with the main line at Wigan.

At the top of the flight, it joins what was once the southern part of the Lancaster Canal, which continues for 10.2 miles (16.4 km) on the level.

[12][13] The ring now follows an active commercial waterway, where narrowboats may meet 600-tonne oil tankers and sand barges.

[14] The ring does not include the navigation below Castleford, where locks were 457 feet (139 m) long, to allow them to be used by a tug and 19 Tom Pudding compartment boats.

[15] Development of the Aire and Calder began in 1699, and continued to be improved at intervals, with the construction of bigger locks and imaginative solutions such as the compartment boats, which resulted in it flourishing until the twenty-first century.

The lower locks were enlarged when the waterway was leased to the Aire and Calder Navigation from 1855, enabling them to accommodate boats of 120 by 17.5 feet (36.6 by 5.3 m), but above Broad Cut Low Lock, they are still 57.5 by 14.2 feet (17.5 by 4.3 m), a size which was originally dictated by the dimensions of keel boats in use on the Humber waterways.

[17][18] To the west of Wakefield, the waterway passes under the M1 motorway, after which the scenery is dominated by the Elmley Moor television transmitter.

[19] The ring continues through Brighouse and past some worked-out gravel pits which are now flooded and used for water skiing.

The final part of the restoration was partially funded by the Millennium Commission, and resulted in the canal being opened throughout in 2002.