In Cheng Po Hung's book, Hong Kong during the Japanese Occupation, he notes that trains started running again on the KCR line in February 1942, but that by 1944 trains only ran once every two days due to fuel shortages. (I guess that train services would have stopped completely by mid-1945 - has anyone seen this confirmed?)
So when the British returned, one of their jobs was to get the trains running again. They didn't waste any time, and the first train ran on the Sep 29, 1945 ... straight into a brick wall!
A film of the day's events has these notes with it:
[...] The train pulls slowly out of the station and a few RAF men dash along beside it. View from the train as it pulls away from the platform. View from the footplate. A man in a topee surveys the scenery. The train, derailed, with Chinese civilians milling about. The locomotive with its nose buried in the ground. [...]
[...] Dopesheet notes that this was the first train to run since the British reoccupation of Hong Kong, and that the derailment was caused by a failure (unattributed to any particular person) to check the points. This sent the locomotive into a siding and crashing through a brick wall. [...]