Steam gave K-class submarines fleet speed at a high price

Why did the Royal Navy put steam machinery into submarines despite the obvious hazards?

The K class was intended to keep pace with a surface battle fleet, and steam turbines offered the surface speed and endurance that contemporary diesel-electric machinery could not.

The K class was conceived as a fleet submarine rather than a slow boat waiting on a patrol line. It needed enough speed and range on the surface to manoeuvre with capital ships, then dive before combat. Steam turbines promised that performance but imposed dangerous complexity when shifting from surface operation to submergence. The concept anticipated nuclear fleet submarines, which later delivered sustained fleet speed without the same steam-and-boiler transition.