Under Edward Thompson, who sought to standardise on the large number of locomotives of the LNER, the L1 was designed to be able to carry out both passenger and goods work.

The running plate features a cutout gave good access to the motion, easing maintenance.

This ranged from style of the cab doors, cylinder linings, boiler pressure to fabricated axle boxes.

Simon A.C. Martin asserts that the reason for the overheating axle boxes was due to leaking water tanks, and that the issue was resolved by making sure they were watertight.

[6] The small 5 ft 2 in (1.575 m) driving wheels limited their maximum speed, but were ideal for accelerating from rest or on gradients, such as the London suburban area.

[5] Coal and water consumption were lower than that of other locomotives, and it was also capable of pulling greater loads.

[7] [2] The prototype was also trialed on coal trains, although its insufficient braking capacity and adhesion mitigated against its use on said services.

[3] During widespread service, they never achieved the same appreciation as the prototype, with complaints such as "shaking themselves to bits", "concrete mixers" and "too small driving wheels".

Due to a lack of improved draughting and fitting of a self-cleaning smokebox, they had to carefully handled by crews.