Formula 1: Mercedes' Paddy Lowe moves to rivals Williams

Paddy Lowe
Paddy Lowe led Mercedes to three drivers' and constructors' championships in a row from 2014 to 2016

Former Mercedes technical boss Paddy Lowe is joining Williams and is set to become a shareholder and director.

The move has been expected but talks have dragged on in recent weeks and at times the deal was at risk of collapse.

But a source close to Williams said they were "in the final stages". Another added Lowe's joining was "a formality".

Lowe, 54, will have a seat on the board as part of his new position, a third source said.

A Williams spokesperson declined to comment; Lowe was unavailable.

The Englishman, one of the most highly regarded and successful design leaders in Formula 1, is expected to be given responsibility for all technical aspects of the Williams group.

paddy lowe and toto wolff
On gardening leave already, Paddy? Toto Wolff and Lowe headed Mercedes as 'executive directors' through a period of dominance for the team

This includes the F1 team but also the Williams Advanced Engineering business, which conducts projects for other companies.

Lowe still needs to formally complete his departure from Mercedes, who announced they had put him on 'gardening leave' pending his exit on 10 January.

Mercedes will consider allowing Lowe to start work immediately once he has agreed terms with Mercedes for his departure from the team, rather than be forced to sit out for a number of months, as is normal when senior F1 technical figures switch employers.

It is not clear at this stage where Lowe's shares will come from. Equity in the team is split between founder and team principal Sir Frank Williams (51%), US businessman Brad Hollinger (15%), co-founder Sir Patrick Head (9%) and an employee fund (4%), with 21% listed on the Frankfurt stock exchange.

Williams and Hollinger were unavailable. Head told BBC Sport he "couldn't comment" on any specifics to do with Lowe's position at Williams.

"Discussions are still ongoing and until a signature is on a bit of paper nothing's a formality, but it would be good for Williams if they can get him," added Head, who stepped down from his day-to-day involvement in the management of Williams in 2011.

Lowe's three full seasons at Mercedes
2014: Mercedes win their first constructors' title (16/19 race wins), and Lewis Hamilton wins world championship
2015: Mercedes win constructors' title again (16/19 race wins), and Lewis Hamilton retains world title
2016: Mercedes win third consecutive constructors' title (19/21 race wins), and Nico Rosberg wins world title

Why is Lowe good for Williams?

Lowe was the technical leader at Mercedes as they took three consecutive world title doubles from 2014-16 after joining the team in June 2013.

The foundations of that success were laid by former team boss Ross Brawn - who left Mercedes at the end of 2013 - but Lowe's leadership, and the consistency of the technical team under him, has seen Mercedes maintain a superiority that has led to three record-breaking seasons.

Lowe started his F1 career with Williams and was central to the creation of the legendary FW14B car with which Nigel Mansell dominated the 1992 world championship.

Mansell in 1992
Lowe rider: At Williams Lowe programmed the computer-controlled suspension which led to Nigel Mansell's dominant 1992 world title win

Under Head as technical director, Lowe programmed the computer-controlled active suspension system which was a key influence - along with the aerodynamic design of Adrian Newey, now technical chief at Red Bull - in ensuring the car was head and shoulders clear of its rivals.

Lowe moved to McLaren in 1993 and was their technical boss when they won their last drivers' world title, with Lewis Hamilton in 2008.

He came close to re-joining Williams during 2012, when current Mercedes team boss Toto Wolff was a director and shareholder, but instead went to Mercedes with Wolff in 2013.

Williams suffered a decline in form the 2000s, but revived to third place finishes in the constructors' championship in 2014 and 2015, before slipping to fifth last season.

Who replaces him at Mercedes?

The reasons behind his departure from his position as Mercedes executive director (technical) are not clear, but the split was initiated by the team.

Wolff and Lowe are said to have been in dispute over Lowe's remuneration and level of authority, and whether his ambitions could be satisfied within Mercedes.

The world champions have recruited former Ferrari technical director James Allison as Lowe's replacement but have not yet officially announced his arrival. Allison, 48, is to join Mercedes in the summer when his gardening leave from Ferrari runs out.

A Mercedes spokesman said: "We ask for your understanding that we cannot comment publicly on confidential contractual details. We have said that we will communicate further information in due course and this remains the case."

Valtteri Bottas
Share and share alike: Williams driver Valtteri Bottas joined Mercedes to replace Nico Rosberg a few weeks ago

View the 2017 F1 race calendar here