The road from Oxford to London has been an important highway for over 300 years. It was made a turnpike in 1718 and over the years the volume of traffic has continually increased. Improvements to the A40 east of Oxford were made in 1957 and 1964 when dual carriageways were built between the Oxford Ring Road and Waterstock Crossroads. This motorway connects the eastern end of this dual carriageway with the existing M40 at Stokenchurch, being the final section of a 50km length of the M40 and completing the provision of a dual carriageway road from London to Oxford.
The M40 up to Oxford was planned with its extension in mind. In the late 1960's, the Ministry of Transport carried out a feasibility study on a new route between Oxford and Birmingham while it was considering the development of a strategic motorway network for the country. It was to provide a direct link from the Midlands and North West to the South coast ports and an added route to London and the South East as an alternative to the M1. In 1972 it was added to the trunk road programme.
The public and representative groups were involved in route planning from the early stages. One of the stretches through which the motorway was likely to pass but which called for sensitive treatment was the section in the Cherwell Valley south of Banbury. Ministers decided to broaden the consultative process on this stretch and in May 1973 the public were invited to comment on three alternative routes. This was the first public consultation ever held on a road scheme and was a great success, generating considerable interest. Public consultation procedures are now a standard part of the development of major new road schemes.
The public Inquiry into the section of M40 between Warwick and the M42 and the linked M42 proposals around the south of Birmingham lasted from June 1973 to January 1974. The Secretary of State announced his decision on the line of the route in 1976. That decision was challenged in the High Court (which quashed the decision) the Court of Appeal and the House of Lords; the final judgement, in the Department's favour, was not reached until 1980. Even then, the decision was taken that this section would not be built until the Secretary of State had approved a bypass of Banbury.
The Department published a draft line for the full length from Warwick to Waterstock in 1981 and The Public Inquiry to consider objections to the line convened in Banbury in September 1982 and closed, after 117 sitting days in June 1983. After further legal processes the line from Warwick to Wendlebury was finally approved and was able to move forward into detailed design and the remaining statutory procedures. The final approvals for these and the statutory procedures for the section from Waterstock to Wendlebury were not fully received until March 1989.