Behind the Belgian coast sat Bruges, eight miles inland and untouchable by naval gunfire. Since 1915 the Imperial German Navy had used Bruges as a U-boat sanctuary, sheltering its submarines in massive concrete bunkers and sending them out to the Atlantic through canals that surfaced at Ostend and Zeebrugge. A U-boat leaving Bruges saved a full day on the run to the Western Approaches, where merchant convoys were dying at a rate that threatened to lose Britain the war. Close those two canal mouths, and eighteen U-boats and twenty-five destroyers would be trapped in their inland fortress. That was the bet. The First Ostend Raid on 23 April had been a disaster - the blockships grounded half a mile from the channel, their crews scuttling them in the wrong place under heavy fire. Ostend was wide open.

Survivors of the April failure came back to plan the do-over. Among them were Commander Alfred Godsal, who would captain Vindictive on her final voyage, and Lieutenant Victor Crutchley, who had served as first lieutenant on the failed Brilliant the first time around. They proposed using Vindictive herself - the battered hero of Zeebrugge, her superstructure punched full of holes from the mole assault - as one of two blockships. Vice-Admiral Roger Keyes and Commodore Hubert Lynes approved. Vindictive's masts were cut down, her remaining guns landed, her hull packed with concrete and explosive charges. A second old cruiser, Sappho, was prepared alongside her. Motor launches would dart in after the scuttling to take off the surviving crews. The whole armada assembled at Dunkirk and waited for weather.

At dusk on 9 May the force sailed. Two minutes after midnight, Sappho's boiler blew and she had to turn back - leaving Vindictive alone as the blockship. Royal Air Force bombers ran a diversion overhead. Royal Marine artillery shelled Ostend from the lines around Ypres. The Germans had pulled the navigation buoys, knowing the British would come again, but Godsal had pored over the charts and thought he could find the entrance by dead reckoning. Then a North Sea fog rolled in and erased the coast. Vindictive crept back and forth across the harbour mouth, looking for the piers. Two German torpedo boats sailed out to intercept her, collided in the murk, and limped back to port disabled. On the third pass, Vindictive finally found the entrance.

The German shore batteries opened up at point-blank range. A shell smashed into the conning tower and killed or wounded most of the bridge crew - including Commander Godsal, whose body was never recovered. Lieutenant Victor Crutchley, twenty-four years old and now the senior surviving officer, climbed to the wheel and tried to swing Vindictive across the channel. A second shell had wrecked one of her propellers; the ship would not answer. Crutchley wrestled her as far as he could and felt her grind onto a sandbank just outside the entrance - blocking it only partly. He ordered Engineer-Lieutenant William Bury to blow the scuttling charges. Then, with a torch, he walked the decks looking for wounded men among the dead before he let himself be lowered down to the motor launch waiting in the lee. For this he received the Victoria Cross, the third awarded for the night.

Motor Launch 254 cleared the harbour with thirty-eight of Vindictive's fifty-five-man crew huddled on her open deck under machine-gun fire. Behind her, the late-arriving ML276 under Lieutenant Rowland Bourke - a Canadian volunteer who had been rejected by the Royal Navy for poor eyesight before talking his way in - heard cries from the water inside the harbour. Bourke turned back in. He searched four times under heavy fire before he found two sailors and Vindictive's badly wounded navigation officer Sir John Alleyne clinging to an upturned dinghy. He pulled them aboard and ran for the open sea. ML276 came back to England with fifty-five bullet and shrapnel holes. Bourke got the second Victoria Cross of the night; Alleyne survived. Offshore, the destroyer HMS Warwick struck a German mine and nearly sank with Keyes himself aboard, listing into Dover the following morning lashed to another destroyer.

Vindictive did not fully close the channel - small craft and submarines could still slip past at high tide - but she stopped the larger warships of Bruges from getting out. Eighteen U-boats and twenty-five destroyers stayed bottled up for the remaining six months of the war. Ostend was liberated by the Allies in October 1918. Three Victoria Crosses were awarded for the second raid - to Crutchley, Bourke, and Lieutenant Geoffrey Drummond of ML254. The British Admiralty presented the operation as careful planning brilliantly executed. The strategic effect on the Atlantic was negligible. The wrecks of Vindictive and her sister blockships at Zeebrugge took until 1921 to fully clear. A bronze section of Vindictive's bow still stands on the eastern jetty of Ostend harbour, where she made her final stand.