Hamilton has worked with Bonnington, known as ‘Bono’ within the team, since he joined Mercedes in 2013 and the pair have formed one of the strongest driver-engineer bonds in F1, winning six world championships together. 

But Bonnington, who has been an integral member of the Mercedes team since the German manufacturer returned to the sport in 2010, is a noticeable absentee from the garage this weekend in Austria. 

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Rather than being on site at the Red Bull Ring, Bonnington is carrying out his usual role from Mercedes’ base in Brackley. 

Hamilton’s regular performance engineer, Marcus Dudley, was heard speaking to the seven-time world champion during Friday’s action and will lead on the radio communications for Hamilton for the rest of the weekend. 

Mercedes have not disclosed the exact reason as to why Bonnington is staying in the United Kingdom, and did not say when approached for comment by Crash.net.

Mercedes boss Toto Wolff stressed that Bonnington remains in constant communication with the team throughout the weekend, despite his physical absence. 

“Bono is not here and that’s always bad,” Wolff told Sky after Friday qualifying. 

"It’s always bad for us as a team because he’s an integral part. Since 10 years, he’s standing to the right of me and I keep watching him. 

“But he’s at home, he’s connected to the intercom. We’re speaking with him all the time and Marcus and Tom are going to do a great job.” 

Hamilton won the last time ‘Bono' was away 

While it is rare not to see Hamilton working with Bonnington in the Mercedes garage, it is not the first time ‘Bono’ has missed a race weekend. 

Three years ago, Bonnington was not present in Mexico City as he stayed at home in the UK to undergo a personal medical procedure. 

He was due to miss two races but returned in time to celebrate Hamilton’s sixth world championship coronation at the 2019 United States Grand Prix.

Despite not having ‘Bono’ by his side in Mexico, Hamilton went on to score his 10th victory of the 2019 season at the Autodromo Hermanos Rodriguez and dedicated the win to his missing race engineer. 

“Bono has been with us in spirit, obviously not here physically but he’s been with us on the radio, in all our meetings, while he’s been at home recovering,” Hamilton said at the time.

“He’s done a huge amount of work before the weekend happened to make sure everyone’s up to speed. 

“This is not an easy job to come and to be the forefront, the number one engineer for a world champion. It’s not easy, there are a lot of demands there and it’s his first time. Him and Dom, who’s my number two, both stepped up to the plate and did a fantastic job.

“Of course I wanted to dedicate this win to Bono because he’s going through - it’s not been the easiest of times. I love the dude. We’ve come a long way together, and I wanted to make him proud this weekend.”

It will take something special for Hamilton to repeat that success at this weekend’s Austrian Grand Prix given he will start only 10th on the grid for Saturday’s sprint race after a heavy crash in qualifying.