Why the Admiralty sold charts beyond the fleet

Does the Royal Navy share its charts with other countries and commercial mariners?

Yes: the Hydrographic Office sells charts internationally, while sensitive survey information can remain classified.

Royal Navy survey data is passed to the UK Hydrographic Office, which turns appropriate material into charts sold around the world. That provides safer navigation for merchant shipping and generates income for the service. Some operational information remains classified rather than entering commercial products. The ships remain naval vessels, although civilian specialists may embark when their expertise is required.