Karting Born in
Dundee, Williamson began karting at the age of eight, and spent a successful decade racing in the various classes around the United Kingdom. By that time, Williamson moved into the junior formulae in 2008, he had claimed three Scottish karting championship titles at Cadet and MiniMax levels, before taking a clean sweep in 2008. The first driver to record such a feat, Williamson won the British Open, British Grand Prix Super Kart, the Scottish Open, as well as the 125 ICC Championship.
Formula Renault After a guest drive in Formula Jedi at
Brands Hatch in which he won one of the two races, Williamson moved up into Formula Renault, contesting the
2008 Formula Renault UK Winter Series after Highland Arena Ltd, an organisation set up by three family friends helping to promote sporting talent from the
Scottish Highlands – where Williamson resides – leased a car from
CR Scuderia. He added another third place in the final race at
Rockingham Motor Speedway, finishing behind Surtees and
Dean Stoneman, to end up in sixth place in the championship standings, a point behind fifth-placed
William Buller. He also contested the
Estoril round of the
Portuguese Formula Renault 2.0 Winter Series, taking second and fifth-place finishes for CR Scuderia. Williamson's Winter Series campaign ruled him ineligible for the Graduates Cup for drivers aged nineteen or under. During the season, Williamson finished 17 of the 20 races, taking a third place at
Donington Park and a second place at
Brands Hatch en route to a tenth place championship finish. Williamson moved to defending champions
Manor Competition for the
2010 season, again as part of a four-car team with
Will Stevens, Thomas Hylkema and Josh Mulholland, with Ollie Millroy replacing Mulholland during the season. In the first round of the season at
Thruxton, Williamson claimed the first pole position, and thus became the first driver to take pole in the
Barazi-Epsilon-designed car introduced for the 2010 season. Several races later at
Brands Hatch, Williamson threw away a chance at his first victory, spinning out of the lead and eventually finishing seventh. The first victory came a month later at
Oulton Park, overtaking
Tom Blomqvist at the start of the first race and was never headed. Williamson took further wins at
Croft and
Silverstone – a rescheduled race from Brands Hatch which Williamson had qualified on pole for – as he and Blomqvist commenced their battle for the championship along with Tamás Pál Kiss and
Will Stevens. Williamson trailed Pál Kiss by 27 points and Blomqvist by 15 before the
World Series by Renault meeting at Silverstone. Williamson won both races from pole position, to trail Blomqvist by one point on dropped scores heading into the final round at Brands Hatch. In the first race, Williamson finished second, ahead of Blomqvist in third, but Blomqvist claimed fastest lap to draw level with Williamson before the final race. In the final race, Blomqvist made a better start and with team-mate Alex Lynn acting as rear gunner, Blomqvist won the championship with his second place. Despite this, Williamson was nominated for the
McLaren Autosport BRDC Award due to his performances in the series. On 5 December 2010, after the evaluation tests held at Silverstone, Williamson was named as the winner of the award, taking the £100,000 cash prize and a
Formula One test with
McLaren.
GP3 Series After the end of his Formula Renault campaign, Williamson took part in the post-season
GP3 Series test in
Estoril, Portugal. Driving for
Atech CRS GP, Williamson set the fastest time in the afternoon session on the second and third days, having arrived at the circuit the day before after a chance conversation with team boss David Hayle. Williamson was eventually signed by
MW Arden to graduate into GP3 in February 2011. Williamson competed in the
2013 GP3 Series with
Bamboo Engineering. He did not compete in the final round at
Yas Marina Circuit, and finished the season in 12th position, his best finish being 3rd place.
Formula Renault 3.5 Series After testing for
ISR Racing during the final test session of 2010, Williamson took part in the opening round of the
2011 season for the team at
Motorland Aragón, deputising for regular driver
Daniel Ricciardo who was on
third driver duties for
Scuderia Toro Rosso at the . == Personal life ==