Why the Royal Navy preferred not to assign a searchlight ship

Before radar, did the Royal Navy use one searchlight ship to keep the rest of a night force hidden?

Generally no. The Navy disliked searchlights because switching one on invited enemy torpedoes toward the emitting ship.

A ship could deliberately expose itself with searchlights while the rest of its formation remained hidden, although the Royal Navy strongly preferred to avoid that method. A visible beam gave enemy light forces a clear point toward which to fire torpedoes. Jellicoe's earlier requirement for safer illumination led naturally toward starshell and illumination by gunfire. The doctrine sought illumination without turning one ship into an obvious aiming point.