George Russell has revealed he first heard he would be Lewis Hamilton’s Formula 1 Sakhir Grand Prix replacement via a 02:00 phone call from Mercedes Team Principal Toto Wolff.

The Williams driver will compete at this weekend’s race after Hamilton was ruled out due to a positive coronavirus test.

Russell beat Mercedes’ reserve driver Stoffel Vandoorne to the drive, despite the latter flying out to Bahrain from the Formula E test in Valencia, leaving the Belgian “hurt”.

Williams agreed to release Russell to the drive, in a deal confirmed the day after Hamilton’s test result was revealed.

The Williams camp moved quickly to announce reserve driver Jack Aitken as the Briton’s replacement.

Speaking to reporters in Bahrain, Russell said he took the call from Wolff while he was in the bathroom.

“I got a phone call from Toto at 02:00 on Tuesday morning,” the 22-year-old explained.

“I was actually in the bathroom, which was slightly awkward. So I answered the phone and he said, ‘George, you in the bathroom?’

“(I replied), ‘Sorry, I’m in the bathroom’. He said, ‘Unfortunately, Lewis has caught COVID. He’s doing well, he’s healthy and feels fine, which is most important, but we want you to drive’.

“(I replied), ‘Right, okay’. And then obviously a bit of a sleepless night.

“We just sort of made it happen throughout the following day. And I counted yesterday, I had 64 phone calls on Tuesday… pinging between so many different people.

“Glad we got there in the end.”

Russell, who has been part of Mercedes’ young driver programme since 2017, admitted he was “very anxious” as he waited for the approval from Williams.

Wolff later praised Williams for its “pragmatic” approach to releasing Russell, who now a golden chance to end his wait for his first Formula 1 points.

While now with the opportunity to drive the best car on the grid, Russell admitted he faces a stern challenge from incumbent Mercedes driver Valtteri Bottas.

“It feels strange to be back with Mercedes as obviously I spent two years there (as) test/reserve/simulator driver,” he said.

“I know all of the guys, which makes things a lot easier to get back into the team.

“Valtteri has been pushing Lewis a huge amount over the years. I know it’s not going to be an easy task coming in.

“Having spent two years in the same (Williams) car with my same engineers, same mechanics and, changing suddenly is (tough).

“Many new things to learn, so I’ve got no expectations, no targets. Just build up to it over Friday, learn as much as I can. Enjoy it, and just do my best.”

Free Practice 1 for the Sakhir Grand Prix will commence at 00:30 AEDT Saturday.