Alex Thomson is out of the Velux 5 Oceans single-handed round-the-world race and was awaiting rescue by his bitter rival, Mike Golding, after serious structural failure with Hugo Boss’s canting keel left him drifting in the Southern Ocean, a thousand miles south of Cape Town.

The safety of the canting keel, which balances the boat in more aggressive angles to the wind, has again been called in question after the serial problems a year ago in the Volvo Ocean Race.

It is one of the ironies of ocean racing that it should be Golding, in Ecover, coming to Thomson’s aid. The two are almost permanently at each other’s throats and cannot mention the other without having a dig. “I refer to them as two randy bulls in a very small paddock,” David Adams, the race director, said before the race had begun in Bilbao.

Thomson, the 32-year-old from Bangor, and Golding, the 46-year-old former fireman from Slough, were neck-and-neck behind Bernard Stamm, the runaway leader in Cheminées Poujoulat. Both had been forced into port for repairs, Thomson to his headsail, after the hurricane force winds in the Bay of Biscay, but had come back strongly.

Thomson’s decision to take the Great Circle route, plunging far southwest of the fleet, looked to have paid off, as he caught the Tradewind earlier and powered into second. But the tenacious Golding reeled him in and the two were separated by just a nautical mile from Stamm before Thomson’s keel failure.

Thomson was 80 miles due west of Golding, who turned back and faced a tricky rescue sailing upwind in 30 knots and big seas. Thomson’s transfer by life raft promises to be a hair-raising experience. Golding was due to rendezvous with Thomson last night. Thomson will transfer with him to the finish of the first leg in Fremantle and Golding will have time lost in the race redressed. Hugo Boss will be left to the ocean.

It is a bitter blow for Thomson, who had to pull out of the Vendée Globe in almost the same spot, almost exactly two years ago, after the base of the mast tore out. He still has not crossed the Southern Ocean. It might have been far worse if he had been more isolated and he was further into a Southern Ocean, which has not yet unleashed its most mighty seas on the leaders.

Hugo Boss was making 18 knots sailing downwind in 30 knots when disaster struck at around 3.30am yesterday. “I was in my bunk grabbing a quick power kip when I was suddenly thrown across the cabin as the boat broached,” Thomson said. “I ran up on deck and went to ease the mainsail but nothing happened. I then went to try and cant the keel, but again nothing happened.

“By this stage the boat was leaning right over on its side with the spreaders in the water, so I went back down below to look inside the keel box. The section which attaches the rams to the keel had completely snapped off and the keel was swinging freely. I took all of the sails down and finally the boat righted itself.”

Hugo Boss is an old 1999 Thomas Lombard design and was formerly known as Sill, but it has been overhauled with a new mast, keel, sails and electronics.

The new keel uses hydraulic rams to cant the keel from one side to another. The keel can be angled 40 degrees into the wind, counterbalancing the heeling angle much more effectively than traditional keels.

Last Sunday, after taking second from Golding, Thomson could not resist a dig. “I have to be conscious of my overall goals: 1. To finish, 2. To learn especially for the new boat, 3. To compete,” he wrote. “Golding will not be happy to be behind me, especially as he had a good 200 miles on me a week ago and is sailing a faster, newer boat. I need to be careful not to be drawn into a 5,000nm match race in big winds and big seas. It would be all too easy to bust something and all three goals would be history. For Golding I guess it’s different. He needs to win, having never won this one or the Vendée before, so I think there’s a good chance he’ll push the guts out of his boat.”

Leaderboard (at 3pm GMT; start in Bilbao on October 22; leg one to Fremantle, Australia, 12,000 miles): 1, B Stamm (Switz, Cheminees Poujoulat) 3,588 miles to finish; 2, M Golding (GB, Ecover) 511 miles to leader; 3, K Shiraishi (Japan, Spirit of Yukoh) 775 miles to leader; 4, R Knox-Johnston (GB, Saga Insurance) 3,090 miles to leader; 5, G Dalton (NZ, A Southern Man-A.G.D.) 3,321; 6, U Barsurko (Sp, Pakea) 3,397.