A number of schemes had been proposed to build a north-south railway route, particularly one connecting the manufacturing districts of the West Midlands and Lancashire to Southampton and the Channel Ports.

From the junction a second section of the SM&AR was to run southwards to join the London and South Western Railway (LSWR) at Andover.

The final section to Andover was to run adjacent to the LSWR main line, but a connection to it there at the point of geographical junction was prohibited.

c. xiii) in July 1878[4][6] The company realised that there was no hope of raising the necessary capital to continue, and planned an altered route with easier engineering.

Never intended as a through line, it was steeply graded and sharply curved, and worked by wooden train staff and ticket, on the time interval system without block telegraph.

[9] The SM&AR was therefore refused permission to open until the GWR (effectively the managing company for the B&HER and the Marlborough Railway) improved the arrangements at Savernake, in particular providing interlocking and the signalling system on the branch.

The act authorised some branches (never built), and was secured in the face of GWR opposition, due to the S&CER's allegiance to the SM&AR and through it to the LSWR.

[4][6][12] The S&CER had been a creature of the SM&AR and had been worked by it, and it was an obvious step to amalgamate; this was done by the Swindon and Cheltenham Extension Railway Act 1884 (47 & 48 Vict.

Apart from the running arrangements over other lines, the new section consisted of 13+3⁄4 miles (22 km) of single track; there were stations at Withington and Foss Cross.

[15] While reaching a connection with the Midland Railway in the north, the company achieved a success in the south: full running powers from Andover to Southampton Docks were granted by an act of Parliament[which?]

The company now had finally achieved the connection to run its own trains between the Midland Railway at Cheltenham, and a port on the English Channel at Southampton.

This showed itself in signalling delays, suggested to be contrived purposely;[16] in restrictions on fares and goods rates, and the potential to veto through charges; and an obligatory ticket inspection stop at Savernake.

A more carefully assembled proposal was put forward in 1894, in collaboration with Henry Brudenell-Bruce, 5th Marquess of Ailesbury, owner of much land adjoining the intended route.

The M&SWJR agreed to abandon a proposed new line from Andoversford to Winchcombe, north of Cheltenham, which would have by-passed the GWR section of route.

The SM&AR purchased three 0-6-0 tank locomotives from Dübs and Company for its opening; numbered 1 to 3 they had 4-foot (1,219 mm) diameter wheels and outside cylinders.

The bankrupt company now had only seven locomotives to operate its extended route, and in 1893 a director, Percy Mortimer, advanced the purchase price of a 4-4-0 tender engine, from Dübs; it became no. 9.

This locomotive, acquired in 1895, became no 14 and had 4-foot driving wheels and outside cylinders, but required some adjustments for use in England including the front buffer beam being mounted slightly above the frames.

[16] In 1897, two 4-4-4 tank engines with 5 ft 3 in (1,600 mm) driving wheels were purchased from Sharp, Stewart and Company; they proved to be useful on stopping passenger trains; they were numbered 17 and 18.

Six 0-6-0 tender engines were purchased from Beyer, Peacock in 1899 and a further four in 1902; they had 5 ft 2+1⁄2 in (1,588 mm) wheels and proved capable on both goods and passenger work; they were numbered 19 to 28.

This is a sophisticated system whose advantage is in handling densely trafficked lines; its complexity was a disadvantage and it was replaced in 1902 with Tyers single-wire three-position block instruments; the latter pattern was being installed on the newly widened double-track sections elsewhere on the route.

"Well I'm damned," said Sid, "what would you have done if the couplings had broken and you were in a water tank at the back of the train going up the bank from Rushey [Platt] to [Swindon] Old Town?

The company was in a poor condition in financial terms: the capital outlay had totalled £2,120,000, and in the best year 1913, cash available for distribution after loan interest, rents, etc., was about £25,000; with several categories of preference shares, this meant that ordinary shareholders had received nothing.

[4] In planning through trains from the North and Midlands to the South Coast, the GWR found the M&SWJR unattractive: it ran towards the south-east, at Andover facing east, and failed to make a useful connection at Swindon.

It also instituted its "economic system of track maintenance" in which there were to be planned gaps in the revenue earning train service to enable permanent way maintenance to be carried out; this was combined with the GWR motor trolley system on the northern section, in which motorised rail vehicles could operate on the line to convey men and materials to work sites.

Savings could have been made by immediately closing the old Marlborough Railway line and the M&GR route, and both Marlborough High Level and Savernake High Level stations, by the provision of a link from the GWR branch to the M&SWJR line at Hat Gate, immediately west of Forest Road overbridge a little west of Savernake stations, where the two routes ran close alongside one another.

There were extensive troop exercise areas and camps on the line, and in addition the north-south link leading to Southampton was heavily used for military purposes.

[6] A large ammunition store was established north of Savernake in July 1940; US troops operated it, supplying armaments during the Battle of the Atlantic, and it later became especially important in the build-up for the Invasion of Normandy in 1944.

At first the base was served by loading and unloading at Marlborough goods yard, but in mid-1943 work started on establishing a rail to road transfer site; the connection was located about half a mile (about 1 km) west of Hat Gate Cottage at a ground frame, and was commissioned on 18 August 1943.

However, on 1 February 1958 the entire line fell to the Western Region, and on 3 November 1958 the remaining trains ran to Cheltenham St James instead of Lansdown.

[34] So far as closed sections are concerned: In January 2019, Campaign for Better Transport released a report listing the line from Swindon to Marlborough as "priority 2" for reopening.