M25, although it is now looked on as an entity for a complete radial route of London, has developed in a piece-meal fashion, with each length having to be proposed statutorily and justified on its own merits. Individual lengths have been taken forward more quickly or slowly according to the problems encountered in passing through the statutory procedures. This has meant that differing lengths may seem to have been brought into service in an apparently haphazard way, but the intention has always been to make the different lengths available to traffic at the earliest opportunity - for the benefit of both the road users and the communities relieved of traffic.

The history of the M25 is interesting in itself, demonstrating, as it does, how thinking changed, over a long period of time, from a series of ring roads to a single orbital motorway. This is covered in the "Origins" page.

The northern and southern sections of M25 were in different Road Construction Regions, and the notes prepared by the co-ordimators for those Regions, which do not pursue much detail, are included for completeness.

The remaining pages give a more comprehensive view of the Planning and construction of the M25. The text and pictures reproduced on these pages are taken from an edition of the Journal of the Institution of Highways and Transportation dated November 1986. Their permission to reproduce these items is gratefully acknowledged.