The M27 was developed from the long-standing route for a new South Coast Road established in the late 1930s, when a new dual carriageway route with at grade junctions was identified by the County Surveyor of Hampshire and used for development control purposes. Residential developments after the Second World War at Chilworth (north of Southampton) and at Paulsgrove (near Portsmouth) were restricted to allow room for a new road. However the restriction of industrial development south of Eastleigh (Southampton) airport was broken during World War II to allow for a large factory extension over the route for the manufacture of Spitfires.
The M27 runs from Cadnam, west of Southampton, to the north side of Portsmouth. Design work was started again by Hampshire County Council on behalf of the MoT when, in 1967, a team of Hampshire County Council engineers who had been working on the design of the M3 London-Basingstoke motorway were transferred to a special office in Southampton. It was subsequently taken over by the Hampshire sub-unit of the South East Road Construction Unit and on the privatisation of the RCU the work was completed by Mott Hay & Anderson (as known then) under the overall supervision of the SE Regional Office. Fortunately for all concerned this was not as complicated as it might appear as the post-war work was carried out essentially by the same people, albeit employed by different organisations.
The principal changes from the early South Coast Road plans included an increase in land take for the dual 3-lane motorway standard and a new vertical alignment to permit the grade separation of side roads and junctions. The Westerly termination of M27 at Cadnam followed an understanding with the Verderers of the New Forest that the motorway should not run through the Forest. The eastern termination of M27 at Portsbridge joined the improved A27(T) which had been routed southwards out of residential development by construction of the Havant and Farlington Cosham bypasses.
To the east of M27 the six mile length of A3(M) from Horndean to Bedhampton takes the route of A3 out of the built-up areas between Horndean and Cosham and was presumably designated as motorway because at that time (1976) it was assumed it would be connecting directly to the M27 motorway. It was completed in 1979. Initially the M27 was destined to be taken at least as far as the Bedhampton junction and, apart from the different coloured signs, the motorist will probably be unaware that it did not happen. However the land acquired for this stretch of the motorway was not quite wide enough - by less than a foot - and the Chief Highway Engineer of the day, quite rightly if a little pedantically, ruled that it didn’t conform to motorway standards and must therefore be an all-purpose trunk road.
In addition to the East West motorway route, urban motorway links were proposed into the city centres of Southampton and Portsmouth. The M271 Nursling Spur linked to Southampton's western docks and the Waterside parishes. A second link was proposed at Stoneham known as the Portswood link motorway which would have become the main access to the city centre and eastern docks. North of Southampton new links at Chilworth and Bassett were included to re-route all trunk road traffic from the north onto M27 in order to remove external traffic from the main city access along the tree-lined "The Avenue" and its adjoining park.
At Portsmouth the interchange included a link northwards to A27 at Cosham and M275 to the South which was planned as the new principal access to the city centre. The whole of this interchange was located within Portsmouth Harbour and required major land reclamation, which is described later.
Between these extremities M27 followed the South Coast Road route except for the section between Hedge End and Fareham which was re-routed southwards in order to provide short links to A27 at Windhover and Parkgate. These were required to serve planned major industrial and residential developments at Parkgate and Fareham Western Wards. Thus, it can be seen that, in addition to replacing the inadequate A27 trunk road, M27 was a vital part of the plan for the development and expansion of South Hampshire.
Draft Statutory Plans for the 30 mile route were published in 1968 and were generally welcomed as demonstrated by a three-week Public Inquiry which dealt with mainly local issues. The Minister of Transport confirmed the proposals in 1970 with the exception of the section north of Southampton which was the subject of a strong objection from the Ford Motor Company who had taken over the aircraft factory. The existence of the wartime legal agreement to protect the route for a new road was not sufficient justification for dissecting a motor vehicle production plant.
A new somewhat tortuous route was developed that avoided the factory by skirting Eastleigh Airport. This was confirmed in 1971 in spite of counter objections by the Airport operator regarding the consequential effect of reducing the runway length. Because of the change in route, it was not necessary for the old Southampton Crematorium to be demolished. However, the topsoil from the garden of rest was removed to a new site constructed on allotment land south of the M27 and north of the South Stoneham Cemetery. All the topsoil was removed by hand to this new location.
Further difficulties followed north of Southampton when, in 1973, the newly elected City Council abandoned the Portswood Link motorway: its construction would have required demolition of over 500 houses. Trunk road connections were then added for "The Avenue" to remain as the principal access from the north, and a much scaled-down conventional interchange was adopted at Stoneham to serve the Airport and to join to a new link road connecting to the existing roads at Swaythling. The Statutory Procedures to implement these changes were completed in the 1978-80 period.