[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".

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.

Following these incidents, Network Rail temporarily closed the line in June 2022 to implement "a permanent fix to keep trains running safely".

[3] The closure was set to last for 9 days and as well as the main task of repairing the cutting near Fareham Tunnel and reducing its gradient, the company sought to carry out 42 other jobs on the line at the same time including winter-proofing the points, clearing litter and graffiti and replacing freight sidings.

[4] The project cost £2.28 million and involved 20 construction vehicles, 10 trains and hundreds of engineers working a combined 7,500 hours, in which 5,000 tonnes of earth were removed from the cutting and an 80-metre long retaining wall was built.

Heavy rainfall caused land movement which was observed by Network Rail engineers, leading to the work that involved drilling 260 steel nails, each one 25 metres (82 ft) long, into the sides of the cutting to prevent the soil slipping onto the railway.

[6] 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.