Romain Grosjean is one of the best drivers on the F1 grid according to his boss at Hethel-backed Lotus, team principal Eric Boullier.

Grosjean's turnaround from 2012, where at one point his first-lap accidents saw him banned for a race and Mark Webber label the Frenchman a 'first-lap nutcase', has been as stark as they come.

And over the second half of the current season, only dominant champion Sebastian Vettel has out-scored his Lotus rival.

Whether it is becoming a father earlier in the year, the confirmed departure of team-mate Kimi Raikkonen or other factors that have helped relax Grosjean, there is no doubt the Finn's team-mate has been in scintillating form of late.

'I'm not sure he has drastically changed,' said Boullier. 'But maybe the final part of the puzzle was needed to acquire the self-confidence he was missing somewhere.

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'These kids, until they get that full confidence, anything can be wrong.

'There is huge pressure to be fighting at the front row, fighting in quali and fighting in the race. We've always known Romain is super fast, actually maybe too fast, sometimes too fast for his car.

'But having this completeness with his family has helped him reach another level of confidence, and then you see the results on track.'

As for Raikkonen's exit to Ferrari – something now complete given the Finn missed Austin and Sunday's Brazilian Grand Prix after undergoing back surgery – Boullier added: 'He is starting to become a damned good driver. I think you can rate him in the top three or four today.

'He started to perform well from Germany onwards. There was still a bit of fine tuning required on his side, but he has had a very fine second half of the season.

'Now he will start next year in a different mood, and we will have a different perspective from him.'