Query: How long is the M25 motorway?
Context: A plan for a comprehensive network of motorways throughout the city (the Ringways Plan) was prepared in the 1960s but was mostly cancelled in the early 1970s. The M25 is the longest ring-road motorway in the world at 121.5 mi (195.5 km) long. The A1 and M1 connect London to Leeds, and Newcastle and Edinburgh.