The motorway was constructed and opened to traffic between 1969 and 1992.
The section from Sunbury to Popham, comprising 4 contracts completed between May 1971 and June 1974, was part of the original London to Basingstoke motorway. Conceived as a trunk road soon after the second World War, and intended to relieve the existing A30 between London and Basingstoke, a large number of potential routes were considered before orders were eventually published, by now for a motorway. Following a Public Inquiry in 1966, the route was fixed in 1967. The motorway was initially being designed by the County Councils as agents to the Ministry of Transport but with the formation of the RCUs in the late 1960s, it became one of the first schemes to be handled by SERCU. An immediate advantage to stem from this much tighter-knit organisation was the work done on the local standardisation of contract procedures. This part of the motorway was opened to traffic in 1974.
From Popham the motorway was planned to be extended southwards to join eventually with M27 to the North of Southampton. Orders were published for the section from Popham to Compton (South of Winchester) and following a Public Inquiry in 1971, the route was fixed in 1973. However, when the Public Inquiry into the necessary side road orders was held in 1976/77, the debate into the route around Winchester was reopened. The length between Bar End and Compton - the stretch which passed through or alongside the water meadows between St Catherines Hill and Winchester - was fiercely opposed. Feelings ran very high and it was at this Inquiry, which ran for more than a year, that the then Headmaster of Winchester College was forcibly ejected along with others for causing a disturbance.
On the Inspectors recommendation the orders were then made for the section from Popham to Bar End, but with further studies to be carried out on the rest of the route. Part of the made route followed the line of the original Winchester By-pass (A33) and required the demolition and replacement of a famous landmark - Spitfire bridge, so called because it was reputed that a Spitfire had been flown under it. The two contracts for the main run of the motorway went ahead without major alarms - there was very good liaison with two local archaeological organisations on a number of interesting finds - and the two lengths of motorway to Bar End were completed in May and August 1985.
The third section of the motorway now became Bar End to Bassett (Chilworth) where it joined M27, although this section in turn broke down into 2 schemes, namely Bar End to Compton and Compton to Bassett (Chilworth), both in their own way very contentious schemes. Following the Inspectors recommendation the Departments consultant, Mott Hay & Anderson, carried out a study in depth of the possibilities immediately to the South of Bar End and eventually proposed a route to the East of St Catherines Hill down Plague Pits Valley, supposedly the burial ground of victims of the great plague. The alternative of following the line of the original Winchester By-pass on the other side of the hill was not recommended because, in order to meet present day standards, some of the water meadows would need to be sacrificed and a large slice taken off the side of the hill. However the one big advantage with the proposal to go to the East of the hill, and one very popular with the locals, was that the old by-pass could be dug up and grassed over so that people could again walk from the town directly on to St Catherines Hill, something they had not been able to do since before the pre-war by-pass was built. It is bizarre that another controversy has started over a proposal by the local authorities to create a large car park for park and ride on this same area of restored open space.
South of Compton the new motorway essentially an upgrading along the line of the old A33 and the problems were the usual ones in this kind of situation of having to squeeze the new road through difficult narrow spaces to the considerable and understandable dismay of the affected frontagers; and subsequently the difficulty of keeping the very high volumes of traffic flowing during the construction work.
The section from Pitmore (Junction 12) to Bassett (Chilworth) (Junction 4 on the M27) was opened to traffic in December 1991. The remaining upgrade of the A33 between Pitmore and Compton, and the new section from Bar End to Compton in June 1995.