Royal Navy captures of enemy equipment and codebooks

How often did Royal Navy ships return with enemy material they should not have been able to obtain?

Often, but no reliable total is offered: sensitive captures such as codebooks were kept secret and remain difficult to research.

Royal Navy ships repeatedly recovered useful enemy equipment and documents, including codebooks. Secrecy makes the extent of those successes difficult to establish. Intelligence historians can struggle to obtain information about the operations even much later. Andy Boyd's research illustrates the sustained effort needed to reconstruct this history.