The M25 is an 117 mile-long orbital roadway which encircles most of the Greater London area.

Originally mostly built as a dual three lane motorway, widening has since taken place in more than half of it – to as much as six lanes in parts.

The idea was first proposed in the early 20th century and then re-mooted several times in subsequent decades before construction began in 1973.

The final section of the M23 was opened by then-Prime Minister Margaret Thatcher in 1986 (it was Europe’s longest ring road when it opened and has since been bypassed by the Berliner Ring).

The M25, which has 31 junctions, is these days one of the busiest motorways in Europe. It connects to 10 other motorways.

Connect Plus – a joint venture between Balfour Beatty, Atkins and Egis – works on behalf of National Highways to manage and operate the M25 network.