Seeing another pattern of smoke floats being laid HMS Anthony came steaming back into the area. The MAD Cats radioed that they were beginning their attack run, and HMS Anthony slowed to seven knots and shifted her course a little away so as not to interfere, although she was about 300m away when Lt Wooley dropped his payload. At 1656 Plane 15 made the first MAD attack run in history, firing 23 of his 24 retro bombs. One had failed to fire.
Ten seconds later Lt Baker's plane passed over the contact point and he dropped a smoke float on the MAD signal, looping round he made his attack run firing all 24 of his retro bombs about 120 seconds after Lt Wooley. Seeing both planes completing their runs HMS Anthony steamed in, laying a pattern of charges on the same point as the two planes had about 20 seconds after Lt Baker.
On U-761 the crew were utterly unaware of what was going on above them. Due to several thermal layers they were having difficulty with their depth. The bow was unexpectedly heavy and so they trimmed her off by blowing air. That's when the bombs started exploding. At 1702 U-761 bobbed to the surface, as she was a lot closer than expected, upon realising their mistake the crew quickly dove her down again.
By now another destroyer, HMS Wishart had arrived and made a depth charge attack, followed closely by HMS Anthony a second time.
On U-761 all the electrics were out, and only emergency lighting was working as well as a host of other damage, including in one compartment the smell of chlorine. At 1710 U-761 surfaced and the crew immediately began to abandon ship. The Chief Engineer attached a scuttling charge to a torpedo in the stern of the submarine. Captain Geider was the last man off, however the Chief Engineer became confused and began to swim towards the stern, he was mortally wounded by the detonation of the scuttling charge, and was rescued by Captain Geider.
At this point a USAAF Ventura and a RAF Catalina appeared and put in attacks on the submarine, at 1717 and 1719 respectively. At about 1720 the submarine sank by the stern, leaving most of the crew in the water. The majority of the crew were rescued by HMS Anthony and HMS Wishart.
Following this encounter the patrol ships covering the Strait were given a more detailed briefing on the system being used, and what to do in its presence. However on March 16th another attempt to sneak into the Mediterranean was discovered. As the MAD Cats worked out their plots a French sloop escorting a French submarine entered the area and despite requests to abort they blithely sailed through the area ignoring all attempts to communicate. However after 30 minutes they re-acquired the track and made an attack. Nearby escorts heard the impacts on the submarine and moved in to also mount their attacks. The submarine never surfaced, but with wreckage and body parts seen in the water it was judged likely the attack had been successful.
The Germans knowing something was up, but not exactly what tried again to sneak a boat into the Mediterranean on May 15th. This time they got two Spanish fishing boats to sail above the submarine. Presumably they assumed it was some sort of acoustic detection that was catching their submarines. However the wooden boats didn't mask the magnetic field of the submarine. The submarine was promptly attacked and after some hits surface vessels were requested. The surface vessels attacks sank the submarine causing a 12 mile oil slick.
Further reading/Image credits:
U-boat Archive has a full stack of documents and photographs, which is too much data for me to reproduce here, on the incident. For example: Want to know what type of camo scheme the MAD Cats had, its all there. It includes full reports from both pilots, and interrogation reports of Cpt Geider.