Opening

Construction of the branch line from Bishopstoke (now Eastleigh) station to Gosport, terminating "outside the fortifications", was approved in 1839. In Portsmouth, there were strong objections to the city being served by a company with rival city Southampton featuring prominently in its name, and so the same act of parliament renamed the company from the London and Southampton Railway to the London and South Western Railway (LSWR).^[1]

Constructed by Thomas Brassey's company, the line was opened on 29 November 1841 but closed four days later due to concerns about the stability of the tunnel at Fareham. In particular the chief inspecting officer, Sir Frederick Smith, remarked that the line at this point passed "through a soil which has baffled all calculation", with the banks of the cutting so steep that "there is scarcely any slope at which it would stand". The line reopened on 7th February 1842.^[1]

Engineering works

The area north of Fareham lies in the Reading clay beds which once supporting a brick, tile and chimney pot-making industry. When constructing the railway tunnel north of Fareham Station the LSWR's contractor encountered numerous problems with flooding and subsidence, and only with much use of bulkhead walls and props could the tunnel be driven through Funtley Hill. In fact, on 15 July 1841 100 feet of the tunnel collapsed while still under construction. Efforts to rebuild the tunnel arch were abandoned after a further land slip on 25 August 1841 and, after the debris was dug out, a short cutting was left resulting in two separate tunnels. Going against the advice of the inspecting Royal Engineer, once the line opened on 29 November 1841, passenger traffic lasted just 4 days before the LSWR's engineer, Joseph Locke, closed the line following a land slip which covered both tracks between the tunnels, during a period of extended heavy rainfall. Goods traffic was reinstated once it was safe to remove the debris but passenger traffic was not permitted until 7 February 1842. The problems with stability continued and the tunnel was relined in the 1870s resulting in special working instructions which required the external lamps then attached to the sides of carriages to be removed for fear of hitting either the tunnels' sides or trains passing in the other direction. When the Meon Valley Railway Act was passed in 1897, it included the 2-mile-long (3.2 km) double-track Funtley Deviation line to be built half a mile to the west of the tunnel to bypass the problem. The tunnel line was retained, initially for Meon Valley traffic only, and singled in 1906 which at least solved the problems associated with reduced clearances (see Meon Valley Railway). On 6 May 1973 the deviation line was closed after it too had suffered from landslips, a serious one in 1962 putting one line out of use, and the new M27 motorway then permanently obstructed the route, save for a pedestrian subway.

The original line remains single between Fareham and Botley and in recent times the line has had to be closed and rebuilt, again due to the clay upon which it was originally laid. In 2019 the cutting south of Fareham no. 2 tunnel (the southerly one) had to be stabilised with several tonnes of bagged ballast and that the northern wing walls of Fareham no. 1 tunnel (the northerly one, further extended by the construction of the M27 between 1973 and 1975) have developed large cracks due to the very mobile soil conditions. It is to be expected that significant remedial work will be required in the 2020s.

Traffic

The line became increasingly important throughout the 20th century as not only did traffic to Gosport and Portsmouth increase, but Southampton's development as Britain's major port for trans-Atlantic liner services meant that the line became busy with traffic from further east on the south coast bound for the port. With the Meon Valley line to Alton opening in 1903 the southern section between Fareham and Knowle Junction became busier still.

Allington station

The Borough of Eastleigh's 2019 local plan discussed the possibility of a new station on the line at Allington, which would need to have "two platforms of sufficient length to accommodate up to 12-car trains" and would cost around £8-9 million. A joint statement from the borough council and Network Rail indicated that it was unlikely the station would be built.^[6]