The British had been alerted to the convoy's sailing by intercepted radio messages. On 15 April, a British Maryland reconnaissance plane sighted and shadowed the convoy. Two Italian SM.79s that were ordered to provide air cover did not arrive, due to the continuing bad weather. During the night of 15–16 April, the convoy was intercepted by the British 14th Destroyer Flotilla ( (flagship), , HMS "Nubian", and , commanded by Captain Philip Mack). At least three of these destroyers were equipped with radar. The encounter took place as the Italian convoy maneuvered around the shallow waters surrounding the Kerkennah Islands.