A20 from Folkestone to Dover is the only non-motorway section of trunk road in the South East Archive since it forms an essential part of the link to the Channel port of Dover. Having taken the decision that the main motorway link from London to Folkestone and Dover should be via M20 rather than M2, it was necessary to provide a high standard link for the final section. However necessary this final link may have been to meet the traffic needs, it was also politically expedient to satisfy the recurring demands, from the port of Dover and from others, that with the arrival of the Channel Tunnel all cross-channel transport modes should be equally well served with good quality approaches.
The motorway, like so many others, was built in stages. The first section was the Maidstone By-pass which was one of the earliest motorways in the country, the contracts having been let in 1958 and 1959 and the two sections opened in 1960 and 1961. The standard was dual 2-lane and this may well have been the case where Ernest Marples, at the opening ceremony, said it would be the last dual 2-lane we would build in the country. (He certainly said it somewhere). Not surprisingly, with the build-up of traffic over the years, especially cross-channel traffic, and the particular problems of conflicting traffic flows into Maidstone at peak periods, a widening scheme became a necessity; and a scheme was commissioned, in about 1986 or 87. The studies soon showed that the straightforward addition of more lanes would not be enough to deal with the conflicting flows and a design incorporating additional lanes on the through motorway together with feeder-distributors for the heavy flows of turning traffic was adopted. Construction took place after 1988.