Mathews made his T20 comeback for Sri Lanka in January after a three-year gap
The 20-year-old beat compatriot Jolyon Palmer, whose father and series director Jonathan was the last Briton to win the Formula Two championship in 1983.
The prize for the Formula two champion is a Williams test as well as the FIA superlicence needed to compete in Formula One.
“Getting into Formula One has always been my dream, and this just brings me one step closer to that,” the Southampton-based driver said in a statement.
“It’s hard to know what to expect but it’s obviously a fantastic opportunity to be testing a Williams Formula One car, so hopefully I can prove myself. I’m just going to go there and do what I do best: get in the car and drive as fast as I can.”
This year was Stoneman’s debut in F2, a recognised feeder series for F1.
In 2008, the Briton drew attention to himself in the Formula Renault UK championship where he ended the season with a better record than compatriot Lewis Hamilton, that year’s F1 champion, had managed in his debut year in the series.
Mathews made his T20 comeback for Sri Lanka in January after a three-year gap
United Nations agency for Palestinian refugees says 80,000 people have fled Rafah since Monday
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The visit was the king's second engagement in two days after he hosted the first annual garden party at Buckingham Palace on Wednesday
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Girl students from the school topped the country in both science and commerce streams