"Grenade" was then transferred to the English Channel and collided with the anti-submarine trawler "Clayton Wyke" on 14 May in heavy fog. Her repairs were completed at Sheerness Dockyard on 25 May. During the initial stages of the evacuation from Dunkirk the ship provided cover in the northern part of the Channel to the evacuation forces and took part in the rescue of 33 survivors on 28 May from the coaster , which had been torpedoed by an E-boat. She made one trip to Dunkirk during the night of 28/29 May and was caught in Dunkirk harbour by German Stukas during the following day. "Grenade" was hit by two bombs which set her afire and killed 14 sailors and mortally wounded another four men. The ship was cast off from her berth, in case she sank there, and then drifted into the harbour channel. The trawler "John Cattling" towed "Grenade" over to the west side of the outer harbour where her magazines exploded later that evening.