Operation Gambit (2-6 June 1944) was one of the smaller operations that made up the D-Day landings and saw ten men in two British mini-submarines spend three days on the sea-floor off the Normandy beaches so that they could transmit a sonar signal to guide the DD tanks onto the right part of the beach.
The plan was for each X-boat to carry its normal crew of four plus one extra man whose job would be to take a rubber boat even closer to the beach to place a final market. X23 (Lt. George Honour) was to mark Sword Beach and X20 Juno Beach. Each carried a radio set mounted under the sub and an extendable mast which would carry a signal lamp to indicate if the boat was in the right place.
The two X-boats left port at 18.00 on Friday 2 June. After a journey that lasted until just before dawn on Sunday 4 June the X-boats reached their destinations, and came up for air and to check their location. They came up again to watch the coast at midday and then at midnight on 3-4 June to listen for messages. Much to their discomfort the crews heard the message indicating that the invasion had been postponed for a day. This meant that they would have to spend the next 24 hours on the sea-bed.
At midnight on 5-6 June the boats came up again, and this time there was no postponement message. At 5.00 they came up again and began to prepare for their task. The rough seas meant that the rubber boat had to be abandoned, and everything relied on the mast. It took twenty minutes to get the mast erected on X23, and at about 5.20am the green light was lit, to indicate that the boats were in the right place, and the radio was turned on.
The crew of the two boats were then treated to one of the most unusual views of the D-Day landings. The massive Allied naval armada slowly came into view, and as the light began to improve the naval bombardment began. Honour and his fellow crewmen found themselves sitting below a massive carpet of 14-inch, 5-inch and smaller shells. This was followed by thousands of rockets from the LCT(R)s, before finally the DD tanks appeared on the scene.
On Juno the tanks were taken close to the shore before being launched, but on Sword Lt Honour got to see the tanks sail slowly past his submarine before turning back to rendezvous with the trawler that took him back to Britain.