British sailor Alex Thomson admits winning the "world's single most difficult sporting challenge" may not be sufficient to quench his desire for success.

Thomson on Thursday launched a bespoke £5.5million boat which he hopes can end his wait for glory in the non-stop Vendee Globe yacht race.

The 45-year-old finished third and second in the previous two editions of the solo around the world competition, having been forced to abandon his initial two attempts due to boat damage.

"I'm not sure I'd be satisfied until I've won the race, and I'm not sure that's a good thing," Thomson told the PA news agency.

"Although I'm aware I am very successful, to me success is defined by winning, so unless I win I'm not sure I will be satisfied.

"But, worryingly, if I win, I'm not sure I'm going to be satisfied. I don't know how that's going to feel.

"That's what I've been trying to do for the past 16 years. We're not far away and we were ahead in the last one so if we can continue with that then we have a real chance."

Yachtsman Thomson still has more than a year of preparation to go until his next opportunity to break French domination of the gruelling 28,000-mile contest.

Construction of his 60-foot carbon fibre boat – named Hugo Boss after the team's principal partner – began in June 2018 and required 50,000 man hours.

The 7.6 tonne black vessel, with striking splashes of fluorescent pink, was built by Hampshire-based Carrington Boats and unveiled in the shadow of Tower Bridge on the river Thames.

It is due to make its racing debut in October during the two-handed Transat Jacques Vabres race from France to Brazil, in preparation for the Vendee – dubbed the Everest of sailing – which starts in November 2020.

Speaking aboard, Thomson continued: "I would describe the Vendee as the world's single most difficult sporting challenge. To my mind, there's no doubt.

"A true test of not only a person's physical strength but more importantly their mental strength.

"So few people have ever done this, less than a hundred. Comparing it to Everest – you can't even compare it any more – 4,000-5,000 people have done Everest now.

"You generally end up with 10 boats that can win, 10 that could podium and 10 that are adventurers.

"And I've got so much respect for the adventurers because I couldn't do it without the competition or the ability to go and win and compete."

After finishing runner-up in 2016-17, Thomson and his team are still searching for a successful blend of sturdiness and speed.

A broken foil ultimately denied him victory on that occasion as Armel Le Cleac'h became the eighth successive French winner in a record time of 74 days, three hours and 35 minutes.

Recent near misses meant Thomson was keen to take more risks with the design of his latest IMOCA 60 yacht in pursuit of a maiden triumph and, currently, he is enthusiastic about the end product.

"You've got to produce a boat that's fast enough to win the race but reliable enough to finish," he said.

"That's probably the biggest challenge we are going to have, getting that equation right.

"Having been third and second, you can now only be measured on being first and then I didn't feel like I had to compromise in any way.

"We often talk about, 'let's not try and hit the ball out of the park', because you might get it wrong.

"Whereas this time I felt like we could, legitimately, and I think we have and so far she's very exciting and performing very well."