British driver Russell, 22, has been snapped up by Mercedes after seven-times world champion Hamilton was sidelined with coronavirus.
Here, the PA news agency looks at the questions surrounding Russell's high-profile drive this weekend.
– What is Russell's background?
Russell was born in King's Lynn, Norfolk. He followed in his brother Benjy's karting footsteps before graduating through the ranks and winning the GP3 and Formula Two championships in consecutive seasons. His impressive performances convinced Mercedes to sign him to their academy. He competed in a number of young driver tests for the world champions, and was signed up by Williams in 2019.
– So, what's his record like in Formula One?
Last weekend in Bahrain, Russell completed a minor piece of history by out-qualifying his team-mate for a 36th successive time – seeing off Robert Kubica over one lap in all rounds of his rookie campaign before outclassing his team-mate for this year, Nicholas Latifi, too. Russell's unbeatable run saw him match a tally set by triple world champion Nelson Piquet between the 1979 Italian and 1982 Belgian Grands Prix. Only Michael Schumacher (56) and Ayrton Senna (44) have beaten their team-mates on a greater number of consecutive occasions over one lap.
– What's his best result?
Despite impressing over one lap in his sub-par Williams machinery, Russell is yet to score a single point in his F1 career, with a best finish of 12th on three occasions. He should have ended his barren run in Imola earlier this year, but crashed out while following the safety car.
– How will he fare this weekend?
Russell is highly rated within the paddock and his unexpected drive for Mercedes this weekend will provide him with the tools to run at the sharp end of the grid. Speaking earlier this year, double world champion Fernando Alonso said of the Briton: "George Russell is the one that surprises me every weekend. He makes zero mistakes and I am really surprised about his natural speed. For the future, Russell is my pick."
Russell will be desperate to enhance his credentials, and while it will undoubtedly take him time to get up to speed in the Mercedes, do not be surprised to see him challenging Valtteri Bottas in the other car.
– And what about his future?
Russell is under contract with Williams for next season, and it is likely he will remain there in 2021. Hamilton's deal expires at the end of this month but it is expected he will agree an extension. Bottas is already signed up for next year. However, a strong performance will increase pressure on Mercedes team principal Toto Wolff, who effectively manages Russell's career, to put the Englishman in one of his cars in 2022.