Sharon & Gordon Thomson wrote:
Have situations ever arisen on London Underground where major service
disruption has resulted from a track problem or derailment occurring
at a critical location at/near a depot such as to prevent lots of
trains from entering service?

25 November 1925 - Lillie Bridge Depot (At that time it was Piccadilly
Line), de-railment on the (at that time) single access road with only nine
trains available to run the morning peak.

Paul B