The M25 motorway was officially opened on 29 October 1986 by Prime Minister Margaret Thatcher.

Key details

  • The opening ceremony took place on the section between junctions 22 and 23 (London Colney and South Mimms).
  • Although various stretches had opened earlier in the 1970s and early 1980s, 29 October 1986 is regarded as the date the complete orbital M25 was opened.