The class, at least on paper, should have been very free steaming and powerful engines but, in practice, they were not suited to the work to which they were assigned. The engines had 5-foot-2-inch (1.575 m) driving wheels, which would give them excellent power at low speed, such as that required for freight work, but these engines were intended for passenger use. The speeds required for suburban passenger work wore the engines out in a remarkably short time. Axleboxes, crosshead slides and crank bearings all suffered due to the high speeds.
On 19 November 1958, a freight train overran signals and was in a rear-end collision with another at Hitchin, Hertfordshire. A third freight train ran into the wreckage and was derailed. Locomotive No. 67785 was pushed over by the wagons from the third train.
In an attempt to reduce wear, two experiments were tried. In May 1951, five locomotives had liners fitted to their cylinders to reduce the cylinder bore from 20 to 183⁄4 in (508 to 476 mm). In March 1953, five locomotives had their boiler pressure reduced from 225 to 200 lbf/in2 (1.55 to 1.38 MPa). Neither experiment was a success.
Boddy, M. G.; Brown, W. A.; Fry, E. V.; Hennigan, W.; Hoole, Ken; Manners, F.; Neve, E.; Platt, E. N. T.; Proud, P.; Yeadon, W. B. (March 1977). Fry, E. V., ed. Locomotives of the L.N.E.R., Part 9A: Tank Engines—Classes L1 to N19. Kenilworth: RCTS. ISBN0-901115-40-1.