The N1 was a development of the basic principles established by the Great Western Railway's (GWR) Chief Mechanical Engineer (CME) George Jackson Churchward and by Maunsell's previous N class design.

[4] It showed a marked improvement in performance over his predecessor Harry Wainwright's 0-6-0 and 4-4-0 designs when tested on freight and local passenger trains.

[4] The success of the prototype encouraged the SECR management to order a batch of 15 in 1919 after government restrictions regulating locomotive production during the First World War were relaxed.

[4] In the meantime Maunsell settled upon producing a 3-cylinder version of the N class 2-6-0, which provided the opportunity to test a variant of the Gresley conjugated valve gear developed by his assistant, Harold Holcroft.

[13] The design utilised the motion of the outside valve rods (the rods transmitting the motion of the driving axles to the valves, such as the combination lever) instead, although the restricted space between the back of the outside cylinders and the front driving wheels made it impossible to locate the rocking arms controlling the conjugating mechanism in the vicinity.

[14] Holcroft's solution was to move the mechanism to a position above the pony truck and ahead of the cylinders and link it to the outside valve rods with extension levers, which had to be accommodated within the strict SECR loading gauge tolerances.

[15] The sides of the outside cylinders consequently sloped inwards towards the top in a configuration similar to GWR 2-cylinder locomotives, thus providing ample space in which to accommodate the extension levers.

[22] A distinguishing feature of the locomotive was the high-set N class boiler, which was pitched 3.5 in (89 mm) above the frames to accommodate the inside cylinder assembly, potentially exposing the conjugation mechanism to the elements.

[19] To prevent corrosion, Maunsell incorporated a vertical metal cover above the front buffer beam to protect the inside cylinder and valve gear assembly, the main visual difference from the N class.

Maunsell was appointed the CME of the new company and embarked upon a greatly expanded programme of fleet standardisation to replace the inherited "pre-Grouping" designs.

822 participated in a series of trials to compare the performance of the N, LSWR S15 and LB&SCR K classes when hauling freight trains of 65 loaded wagons between Woking and Eastleigh.

[24] Despite achieving the lowest coal consumption per mile of all the designs tested, the N1 prototype cost more to maintain and displayed poor steaming qualities that affected timekeeping.

[25] The Southern Railway had also upgraded the permanent way on many of the former SECR routes by 1929, removing many of the weight restrictions that inspired the use of the Holcroft gear in the first place.

[25] Maunsell was therefore free to use three separate sets of Walschaerts valve gear driven by the centre driving wheels and the crank axle, a system that was easier to maintain due to the wide availability of parts.

[26] Other variations included a set of footsteps beneath the front buffer beam, reversion to the N class cast chimney design and a revised dome that incorporated the regulator to ease access during routine maintenance.

[12] Despite the high maintenance costs and steaming difficulties revealed during the 1924 freight trials, the N1 prototype compared favourably against the N class, allowing the Southern Railway's management to order the final five locomotives in 1929.

A876–A880 were initially allocated to the Central section shed at New Cross, from where they were regularly used on through expresses from the LMS between Willesden Junction and Brighton and services to Hastings and Bognor Regis.

[19] The class was re-allocated in 1935 with three based at Eastbourne on the Central section to haul through trains to the GWR and the London, Midland and Scottish Railway (LMS).

[32] This resulted in improved riding characteristics on the footplate at low speeds whilst reducing mechanical wear and the effect of hammerblow on the track.

822 suffered under a poor maintenance regime caused by the difficulty and expense of producing non-standard spare parts at Ashford works.

[1] Other modifications included moving the regulator valve from the smokebox to a new N class-type dome to ease access during routine maintenance and the addition of a front footstep behind the bufferbeam.

[25] The result of the various modifications was a heavier locomotive, although it now benefited from upgraded track on the Eastern section and the interchange of standardised parts that reduced the time needed to complete repairs.

[29] The reduction of work over the Brighton Main Line and the prevalence of the N class precipitated another move to Stewarts Lane shed in London.

[22] The repainting took place during essential maintenance visits to Ashford works, and included the application of Bulleid's "Sunshine" yellow block lettering and numerals on both tender and cabside.

[9] When repainted to Maunsell's dark olive green livery, a prefix "A" was applied to the number to denote a locomotive allocated for overhaul at Ashford.

[22] Shortly thereafter the prefix was dropped and 1000 added to the numbers as part of a general renumbering of Southern Railway locomotive stock; thus on the rebuilding of the prototype in 1930 it became 1822.

[36] The N1 was a capable class of mixed-traffic locomotive that could operate over the Southern Railway's gauge-restricted routes and was noted by crews for its comfortable riding qualities.

[27] However, the prototype offered little improvement in performance over the N class when tested on non-restricted routes, which led to an initial reluctance within the management of the Southern Railway to authorise batch construction.

[1] The prototype was rebuilt to the same specification as the 1930 batch, creating a robust workhorse capable of a good turn of speed when working heavy passenger and freight trains.

[3] The relatively early withdrawal of the N1s pre-dated the era of preservationists buying withdrawn locomotives from scrap dealers or British Railways, and consequently no examples of the N1 class survived into preservation.