A failed withdrawal and Beatty's career

If Beatty had turned away at Cadiz, would he have faced court martial or execution?

Probably not for cowardice, but an effective bar on future sea commands could have capped his career and prevented his later promotion to First Sea Lord.

The answer separates a formal accusation of cowardice from the career consequences of an unsuccessful withdrawal. With Beatty's ships already lost in the counterfactual, a cowardice finding would be difficult to sustain. Ernest Troubridge's treatment provides the more likely model: censure followed by a ban on further seagoing commands. For a vice-admiral, that restriction would effectively cap advancement and close the route to First Sea Lord.