Alonso's engineer joins Williams

Sources have told autosport.com that Nelson has been appointed Williams's chief race and test engineer, working closely with technical director Sam Michael.

The aim is for Nelson to take some of the on-track responsibilities away from Michael, freeing him up to focus more on the car design.

Williams co-owner Patrick Head said earlier this year that Michael's role was going to be redefined for 2007 to allow such a situation to happen.

"An F1 team is a big and complex organisation and you have to have many aspects," said Head. "You cannot have one person leading all the activities that are going on.

"Sam has been doing a lot of rethinking and he is changing his focus so that he comes out of operations. He has been a data engineer, a race engineer, a senior operations engineer and then became a technical director.

"I think in truth his focus probably stayed a bit too much on the operations side and not enough around the factory, which is where performance, speed and in truth reliability comes from."

Nelson's capture is a coup for Williams, with the respected engineer having helped guide Alonso to the last two world championship crowns.

Although the exact reasons for the move have not been confirmed, sources have suggested that Nelson was not amused by the future staffing reshuffle planned at Renault - especially that Giancarlo Fisichella's race engineer Alan Permane had been promoted to chief race engineer rather than him.

Williams declined to comment on the appointment, while Renault were unavailable for comment.