M4 motorway M4 motorway The M4, a motorway in the United Kingdom running from west London to southwest Wales, was originally referred to as the London-South Wales Motorway. The English section to the Severn Bridge was constructed between 1961 and 1971; the Welsh element was completed in 1993. The Second Severn Crossing officially renamed the Prince of Wales Bridge, was inaugurated on 5 June 1996 by HRH The Prince of Wales and the M4 was rerouted. Apart from its two spursthe A48(M) and the M48the M4 is the only motorway in Wales. From London to Bristol, the M4 runs close to the
M32 motorway opened by the Secretary of State for Transport, John Peyton in July 1970. The total cost was £3 million (now £ million). In 1972, a polystyrene storage depot on Muller Road near junction 2 caught fire, leading to the closure of the southbound M32 for six days. The third section was the most technically demanding, as it ran through heavily built-up urban areas and required numerous properties to be demolished, along with the "Thirteen-arch viaduct" near Stapleton Road that was built in 1874. Work was delayed owing to the Three-Day Week industrial action in 1974, and further because of a