Don't forget HMS Cumberland playing herself, but highly modified as a gunnery trial ship without her 8in turrets.

HMS Ajax played by HMS Sheffield
HMS Exeter played by HMS Jamaica
HMNZS Achilles played by herself (then INS Delhi)

USS Salem as DKM Graf Spee: as the US Navy wouldn't allow a nazi flag on an american cruiser, all shots displaying it were filmed aboard a british ship.

Note also two, then, "almost unknown" actors:

- Christopher Lee as Manolo the bar tender. This was his 38th movie but the first with consistant role (i.e. with more than a few word of text). A comical role, very far from Dracula, the year after.
- Patrick "John Steed" McNee as Lieutenant Commander Medley aboard HMS Ajax : his 14th movie, another one of the numerous small roles in his early career. During WW2 he had served in the RN on MTB in the Channel.