Alex Thomson appeared to be out of miracles last night and it seems he will be forced to withdraw from the Vendée Globe race this morning after an assessment of the damage to a cracked hull by his shore team.

The Briton was catching up on sleep as Hugo Boss was lifted out of the water off Les Sables d'Olonne and the extent of the damage became obvious. The port-side crack was worse than was feared. It is five metres long through the honeycomb of the aramid core, all the way back to the stern of the boat. Unusually long strands of carbon fibre from the outer shell trailed down from the hull.

“In the timescale available to us to restart the race, we would have to do a full structural survey of the boat, put together a full repair plan, which in itself is a very difficult task, and then put a team together the size of which we had for the repair three weeks ago,” Harry McGougan, Alex Thomson Racing's operations director, said.

Thomson had a frustrating 5-hour wait for the tide to allow him back into port yesterday. He will make the final call on whether this is all possible given the deadline of midday on Wednesday, November 19, ten days after the start last Sunday. But getting together the team of 42 that fixed the hull on the starboard side and recast the mast, after being hit by a fishing boat, and doing the work in time looks impossible. Thomson, 34, would have to overrule those who, by his own admission, have a much better understanding of the structural complexities of his boat.

The reason for the crack remains unclear, but Paolo Manganelli, from Gurit, the boat's structural designer, agreed with McGougan that Hugo Boss may have hit something.

Pascal Conq, one half of Finot-Conq, the French team that designed the boat and are behind four of the five Vendée Globe winners, was also not optimistic. “I was very confident about the repair and the repair hasn't broken, but it is something that we perhaps missed,” he said. “I don't know if, together with the impact of the fishing boat, it's possible. It could be something that happened very far from the impact point.

“We have seen something strange as it [the crack] is exactly in the position of the cradle where we put the boat after it had been hit by the fishing boat and it was not exactly a good cradle. Something could have happened. I think it is a bit too late. For me it will take too much time, so it is not easy to imagine [being able] to start again. The crack is visible, but the problem is to see all the things that are invisible.”

Thomson would stand no chance of winning. The fleet will be a thousand miles away this morning and is too big this time for them all to drop out. Sébastien Josse, on the British-built BT, was back in the lead by yesterday evening, but the first 14 boats are within 70 miles of each other as they dive south downwind towards Madeira. Mike Golding, on Ecover 3, was the leading British boat, 57 miles behind.

Josse was further east of the fleet, touching the high-pressure system in the Azores, and should be able to gybe before those closer to the coast of Portugal, who are sailing the more direct route. As ever, it is about speed versus the most direct route, what sailors call VMG, or velocity made good.