The implementation of the northern half of the M25 was the responsibility of the Eastern Road Construction Unit up to 1981 and the Eastern Regional Office (Transport) from then onwards to completion in 1986. Although the M25 London Orbital Motorway was the number one priority of the programme of successive Governments, each section had to be presented for public scrutiny and comment on its own merits.
The M25 had a long and controversial history in its making. The idea for an orbital road for London was promoted as a matter of urgency in evidence to the Royal Commission on London Transport in 1905. Mr Rees Jeffreys, subsequently Secretary of the Road Board, commented that "it was a disgrace that no road existed which encircled the English capital city". He added "while tram, railway and road communications should all be considered together, the most urgent need is for a circular road". (Was this the germ of integrated transport policy?).
The 117 miles of the M25 makes it the longest city bypass in the world. It has attracted continued public interest, favourable and unfavourable. The vast majority of travellers delayed by the huge volumes of traffic - and those who consider it the longest car park in the world(!) - will not be aware that the cause is democracy over the years which has whittled down the Abercrombie Plan in 1944 for A,B,C,D and E rings around London to a combination of D and E (the M25) and half of C (the A406 North Circular Road).
The archive contains many varied documents, including papers to professional bodies explaining how problems have been resolved so that others might benefit if they encounter similar problems.
The northern half of the M25 contains four major motorway-to-motorway interchanges which are included in the archive material. The M40 Interchange (Junction 16) in the Alderbourne Valley had to be unobtrusive and provide free flow for the high volume of traffic between M40 west of the interchange and M25 south, resulting in a two-level interchange with larger radius curves for these movements and tighter loops for the remainder.
The M1 Interchange (Junction 21) is a four-level structure to reduce the visual effect of the interchange on its surroundings, with extensive contouring and planting incorporated.
The A1(M) Interchange (Junction 23) required enlargement and rearrangement of the existing roundabout between A1(M), M25 and A6.
The M11 Theydon Interchange (Junction 27) incorporates two levels to keep to the minimum its effect on the valley and has seven bridges to provide two-lane free flow in all directions.
The archive also includes the major features of Holmesdale Tunnel in Waltham Cross to reduce the effect of the motorway on this urban area and Bell Common Tunnel in the northern tip of Epping Forest to restore the forest and a cricket pitch.
A happy coincidence occurred for one of the contractors when the final length of M25 was opened by the Prime Minister Rt Hon Margaret Thatcher in October, 1986. Balfour Beatty had built the first 2.7 mile length of M25 opened in 1975 between South Mimms and Potters Bar (Junctions 23-24) and had also built the adjacent length of 3.8 miles between London Colney and South Mimms (Junctions 22-23) opened 11 years later.
It was announced at the opening that problems of peak hour congestion were being tackled, including the provision of a fourth lane between Chertsey and Yeoveney (Junctions 11 and 13).
The Department of Transport produced a 56-page illustrated brochure to commemorate the opening which is in the archive. This contains details of the contract lengths.
In 1989 the Department of Transport published "M25 Review Summary Report" prepared by Rendel, Palmer and Tritton, Consulting Engineers. The report provided the result of an objective assessment of current andfuture traffic demands on the M25, the extent of congestion and suggestions on the measures which might be provided to relieve congestion and delays. The report indicated that the M25 is one of the busiest lengths of motorway in Great Britain. By October 1987, the average weekday traffic flow on a typical section was 101,000 vehicles per day. The M25 represents 6% of the total length of Britain's motorways. The high usage, however, constitutes 15% of all motorway travel. It is ironic that during Public Inquiries after the oil crisis of 1973 objectors to the proposals for the M25 claimed that the traffic forecasts of the Department of Transport were too high.