Following World War II, the Ministry of Transport planned a large-scale upgrade of the A30 across south-west England, with the eventual intention that most of the route would be at least dual-carriageway. The M3 motorway was planned as a replacement for the A30 between London and Popham. Following a public enquiry in 1966, the line was fixed the following year. The work was completed as far as Bagshot in 1971, then to Sunbury-on-Thames in 1974. In 1971, the Secretary of State for the Environment, Peter Walker announced many upgrades of the A30 across Devon and Cornwall, identifying the section from Okehampton to Bodmin as a key area of improvement.