Article snapshot taken from[REDACTED] with creative commons attribution-sharealike license.
Give it a read and then ask your questions in the chat.
We can research this topic together.
These were powerful locomotives but even more power was required so, in 1930, one locomotive was fitted with a superheater and a booster engine and classified S1/2. Two new locomotives (with superheaters and boosters) were built by the LNER in 1932 and classified S1/3. The remaining (non-booster) locomotives were classified S1/1 and were also fitted with superheaters. All the boosters were removed in 1943.
All six locomotives passed into British Railways ownership in 1948 and were numbered 69900-69905.
Yeadon, W B (1996). LNER Locomotive allocations 1 January 1923. Oldham: Challenger Publications. p. 10. ISBN1-899624-19-8.
Ian Allan ABC of British Railways Locomotives, part 4 (1948 ed.). p. 56.
Casserley, H.C.; S. W. Johnston (1974) . Locomotives at the Grouping 2: London & North Eastern Railway. Shepperton, Surrey: Ian Allan Limited. ISBN0-7110-0553-2.