Claire Williams has admitted that her team owed it to Valtteri Bottas to allow him to take Mercedes drive having previously blocked his move to Ferrari.

Though Bottas was strongly linked with Ferrari in 2015 as the Italian team sought a replacement for Kimi Raikkonen who might push Sebastian Vettel ever harder, the reason why the move didn't come off has never been made clear.

Speaking on the day the first pictures of her team's 2017 contender were made public, Claire Williams has admitted that the Grove team blocked the move and it is because of this it was felt Bottas was owed the opportunity to fill Nico Rosberg's newly-vacant seat at Mercedes.

"Valtteri has been an important part of Williams," she said of the Finn who joined the Grove team as test driver in 2010, finally making his (F1) race debut in 2013, "he's got that fiery passion that you want in a driver because all he wants to do is be in the best car and win.

"We stood in Valtteri's way once, when Ferrari came along," she told Autosport, "and I made a promise to Valtteri I wouldn't stand in his way again... I honour my promises.

"When you have a driver that you know that's all they want, why force them to race your car?" she continued. That's not the right thing to do. He has an amazing opportunity, and it will be interesting to see how Valtteri does this year."

However, there remain fears that allowing Bottas to leave and replacing him with Felipe Massa, who had retired from the sport, albeit unwillingly, and partnering the Brazilian veteran with a rookie (Lance Stroll), sends out the wrong message in terms of the Grove outfit's ambitions.

"We made sure it could work for us," she said. "I have total confidence in the decision I made. I think we did the right thing, and I have no regrets.

"Anyone who knows me will know I did a good deal for this team," she insisted, "and I would only have made that move if it was in the best interests of the team. Everyone knows how much I love this team, how important this is to me and how much I want it to get back to winning.

"I'm looking forward to seeing what Felipe can do," she said of returnee Massa, "I hear that fire in his voice again. The pressure is off. He's coming back for a swansong and he can have good fun."