Two British destroyers were torpedoed during the Dunkirk evacuation. Both were sank in relatively quick succession; the second was sunk while trying to rescue survivors from the first. The old destroyer Wakeful, constructed in 1917, was the first target, with the newer Grafton being the second.

On the 28th May 1940, Wakeful arrived off the beaches, her second trip to Dunkirk. Some 640 soldiers were taken on board, mostly using the ship's boats, as well as small craft obtained by the soldiers ashore. She departed the beach after sunset, and followed Route Y, the easternmost of the three safe routes away from the beaches. At about 00:45 on the 29th May, as she approached the Kwinte Whistle Buoy, her lookouts sighted two approaching torpedoes. One was avoided, but the other struck the ship just ahead of the boiler room. The torpedoes had been launched by the German motor torpedo boat S30, which had been hiding behind the buoy and waiting for just such an opportunity. The torpedo blast cut Wakeful in two. Both halves sank quickly, though in the shallow water, the intact ends remained out of the water for some time. The troops had largely been taken below, to reduce the ship's topweight, and hence make capsize less likely; as a result, only ten soldiers made it off the ship. There were also ~50 survivors from her crew in the water, plus more clinging to the wreck. Unfortunately, several of these would be killed in the course of events.

There was a strong tide running at the time of Wakeful's sinking, and the survivors in the water were soon swept away from the wreck. Fortunately for them, they were picked up by two drifters (fishing boats commandeered by the RN), the Comfort and Nautilus. The Nautilus headed on to Dunkirk, but the Comfort headed back to the wreck of Wakeful to search for more survivors. This was at the instigation of Wakeful's captain, Commander Fisher, who had been brought aboard Comfort. Comfort arrived on the scene of the wreck at about the same time as Grafton and the minesweeper Lydd, about 02:40 on the 29th. Grafton stopped to pick up survivors, while Lydd made to watch out for submarines and surface craft. Fisher ordered Comfort to come alongside Grafton, in order to warn her of the risk of torpedoes. As she did so, there was an explosion on Grafton's bridge, killing her captain and several officers; the precise cause is unknown, but may have been a 20mm shell fired from an MTB or other surface craft. Almost immediately after this, Grafton was struck by a torpedo. This had been fired by the German submarine U-62, which had been patrolling the area, to limited avail, for several days. The torpedo hit destroyed Grafton's stern, and caused chaos amongst the British ships in the area. Comfort was mistakenly identified as an MTB, and fired upon by Grafton and Lydd (which also rammed her). This friendly fire killed many of her crew, and the survivors of Wakeful aboard her, though Commander Fisher would survive. Grafton sank slowly, and most of her crew, plus the soldiers aboard, were taken off by other ships. Once this was complete, she was finished off by gunfire from the destroyer Ivanhoe. Sixteen of her crew died, four of whom were killed on the bridge. Some thirty-five Army officers also died, having been killed when the torpedo blast destroyed the wardroom (officer's quarters) where they had been berthed for the trip.

The destroyer seen in the film Dunkirk is the French destroyer Maillé-Brézé. Built in the 1950s, she is a much later design than either of the two British destroyers torpedoed at Dunkirk. She is now a museum ship in the French city of Nantes. The sinking of the ship in the film seems to track more the sinking of Wakeful, though it's only loosely based on the historical event.