Russell was given the all clear by Williams for a potential one-off drive with the world champions but admitted the initial contact had come in unusual circumstances.
“I was actually in the bathroom, which was slightly awkward,” he said. “Toto [Mercedes’ team principal] said, ‘George, are you in the bathroom?’ and I said I am. He said, ‘Lewis has Covid, he’s doing well and feels fine, which is most important, and we want you to drive’.”
The drive, though, was far from a one-call arrangement, with Russell saying he had 64 phone calls in all the following day before the deal got over the line.
The Briton admitted that stepping into the shoes of his countryman, who has won 11 races this season, was a difficult task for two reasons.
“Stepping into his shoes, into his car that he won the world championship in is obviously surreal – it’s the hardest shoes ever to fill,” he said.
In addition, Russell has gone down a boot size from his usual 11s to squeeze into the cockpit. At 6ft 1in, he is five inches taller than Hamilton and admitted getting into the car had been a “tight fit”.
He added: “That’s slightly uncomfortable but I am sure I can endure the pain for this opportunity.”
As for his race chances come Sunday, Russell said he has not ruled out the possibility of victory.
He said: “You’ve obviously got to believe. I’ve been given an incredible opportunity but I’m not setting any targets. I’m just going to give it my all.”