The core section between London Euston and Glasgow Central is 399 miles (642 km) long, with principal InterCity stations at Milton Keynes Central, Rugby, Stafford, Crewe, Warrington Bank Quay, Wigan, Preston, Lancaster, Oxenholme, Penrith and Carlisle.
The central core has branches serving the major towns and cities of Northampton, Coventry, Birmingham, Wolverhampton, Stoke-on-Trent, Macclesfield, Stockport, Manchester, Runcorn, and Liverpool; there is also a link to Edinburgh, but this is not the direct route between London and Edinburgh.
The route between Rugby and Birmingham, Wolverhampton and Stafford was the original main line until the Trent Valley Line was built in 1847. South of Rugby there is a loop that serves Northampton, and there is also a branch north of Crewe to Liverpool which is notable since Weaver Junction on this branch is the oldest flyover-type junction in use. A loop branches off to serve Manchester, another between Colwich Junction in the Trent Valley south of Stafford via Stoke-on-Trent, one north of Stafford also via Stoke-on-Trent, and one via Crewe and Wilmslow. A further branch at Carstairs links Edinburgh to the WCML, providing a direct connection between the WCML and the East Coast Main Line.
The geography of the route was determined by avoiding large estates, and hilly areas, such as the Chilterns (Tring cutting), the Watford Gap and Northampton uplands followed by the Trent Valley, the mountains of Cumbria with a summit at Shap, and Beattock Summit in South Lanarkshire. This legacy means the WCML has limitations as a long-distance main line, with lower maximum speeds than the East Coast Main Line (ECML) route, the other major main line between London and Scotland. The principal solution has been the adoption of tilting trains, initially with British Rail's APT, and latterly the Class 390 Pendolino trains constructed by Alstom and introduced by Virgin Trains in 2003. A 'conventional' attempt to raise line speeds as part of the InterCity 250 upgrade in the 1990s would have relaxed maximum cant levels on curves and seen some track realignments; this scheme faltered for lack of funding in the economic climate of the time.