Why British industry could build giant dockyard cranes

Could British industry build dry-dock gantry cranes on the scale used at major continental yards?

Yes; it would be difficult and expensive, but the necessary heavy-engineering capabilities already existed.

The answer treats a giant dockyard gantry crane as demanding but conventional heavy engineering. Britain already possessed the constituent knowledge used in large trestle bridges and other industrial structures. Combining those capabilities at a shipyard would be possible. The limiting issue was whether anyone would provide the money, effort, and site development needed to install it.