How large a Royal Navy ship could use the Caledonian Canal?

What is the largest Royal Navy vessel that could pass through the Caledonian Canal?

Probably a River-class patrol vessel, although the estimate is tentative because canal condition and draught may impose tighter limits.

A River-class patrol vessel is the tentative upper limit for a Royal Navy ship using the Caledonian Canal. The canal's condition and local draught constraints may make even that estimate optimistic. A frigate or still larger warship would be too risky without much firmer information. The exchange shows how waterways, maintenance, and depth can constrain naval movement independently of a ship's combat capability.