In 1652 he was captain of the "Andrew", and in May was senior officer in The Downs, wearing a flag by special authority from Blake, when, on the 18th, the Dutch fleet under Maarten Tromp anchored off Dover. It was thus Bourne who sent, both to the council of state and to Blake, the intimation of Tromp's presence on the coast, and who commanded that division of the fleet which had so important a share in the Battle of Dover.