The Adams T1's 5 ft 7 in (1,702 mm) wheels had been developed to meet the LSWR's requirement for a compact and sure-footed suburban passenger locomotive to be utilised on the intensive commuter timetables around London.

[1] Some sources record these locomotives as X14 class,[3] and this designation was sometimes used to refer to the longer-framed versions,[7] but for most purposes the two sub-classes were grouped together and known as M7.

The 1904/05 construction batch moved the sandboxes back to the front splasher and new items were feed water heating, single ram pumps and balanced crank axles.

After 1912, thirty-one M7 locomotives were equipped with push-pull train capabilities with the provision of a primitive cable and pulley device.

[1] This was a modification that was designed to save time on country branch lines where the locomotive would usually have to run around its train in order to make a return journey.

As a result, it was possible for the driver to drive his train from a cab located at the front of a designated push-pull coach, leaving the fireman to tend the fire and operate the injectors on the locomotive footplate.

[1] Because the air compressor required extra space for installation, these conversions were confined to the long-framed members of the class.

[2] This was the result of short-framed M7s having long frames substituted during overhaul in order to create room for the air compressor.

[5] When first introduced to LSWR, several of the class were allocated to work semi-fast passenger services between London and Portsmouth, Exeter and Plymouth, and Bournemouth and Weymouth.

However they were withdrawn from these duties after a high-speed derailment near Tavistock in 1898, following criticism by the Board of Trade inspector about the use of front-coupled locomotives on fast services.

[5] As a result, the class was to become synonymous with local main line and branch workings, as well as London suburban services.

[5] Others remained in the London area on empty stock workings, notably between Clapham Junction and Waterloo station.

During the time it was in steam 30245 travelled to open weekends under its own power as well as making an appearance at London Waterloo in 1988.

When transferred to Southern Railway ownership after 1923 the locomotives were outshopped in Richard Maunsell's darker version of the LSWR livery, with numbering having an 'E' prefix to denote Eastleigh.

[10] With the appointment of Oliver Bulleid as Chief Mechanical Engineer of the Southern, livery policy was changed once again to malachite green for major passenger locomotives, with Sunshine Yellow lettering.

During the war years the locomotives were outshopped in wartime black after overhaul, and some of the class retained this livery to nationalisation.

After the war, four Nine Elms locomotives (38, 242, 243 and 244) were turned out in fully lined malachite green for Waterloo station pilot duties.

[2] Livery remained Southern black, though two malachite locos which were painted soon after (numbers 30038/30244) were lettered for British Railways in yellow Gill Sans style along the sides of their tanks.