On 3 July she was present at the attack on the French fleet at Mers-el-Kébir (Operation Catapult). On 6 July she formed part of the escort with the ships of the 13th and 8th Destroyer Flotillas for the battlecruiser , the battleship , the aircraft carrier and the cruisers and for the air attacks on the . "Vortigern" then joined the destroyers , , , , , , , "Velox" and on 8 July as they screened the capital ships preparing for air attacks from HMS "Ark Royal" on Italian targets on Cagliari. The operation was abandoned after the force came under heavy air attack, and "Vortigern" took passage to Britain on 12 July.