Lewis has been racing since he was 8 years old, starting out in karting as a Cadet. He made an immediate impression winning several novice trophies early on, moving swiftly through the junior classes and collecting several Scottish Championship and Super Series titles on the way. Lewis quickly progressed to senior level where he competed in various British Championship events in the 125 ICC class. He swept the boards winning every championship he entered. Lewis' next opportunity was a guest drive in a Formula Jedi - a gift from Alan Dallas of Ross-shire Engineering. He qualified in pole position and won the race, his first ever time in a car against a competitive field of 24.
Thanks to the support of Highland Arena and its sponsors, Lewis was given the opportunity to test a Formula Renault with CRS Racing, which he grabbed with both hands. On the back of this, Lewis was allowed the privilege of competing in the Winter Series. He achieved two podium finishes and finished 6th overall. He also competed in a round of the Northern European Championship in Estoril, where he qualified in 2nd place and finished in 2nd place, against some of the top competitors in Europe. His success in Formula Renault caught the attention of the BRDC and after a recommendation, Lewis was invited to become a member of the British Racing Drivers Club Rising Star programme.
Lewis began the 2009 Formula Renault UK championship with CRS Racing at Brands Hatch and finished in 4th place in his first race. During Round 6, at Donnington Park, he made the podium with a 3rd place finish and received the Driver of the Day award for his efforts. Lewis ended the season with 2nd and 4th place finishes on the Brands Hatch Grand Prix circuit and finished 10th place overall in the Championship.
For the 2010 Formula Renault UK Championship Lewis made the move to Manor Competition and secured five race victories - including a memorable double at Silverstone Grand Prix circuit in front of more than 120,000 spectators. He won more rounds than anyone else along with five pole positions and four NGK fastest laps. Lewis ended the season just missing out on the championship, going into the final race on equal points. The season was rounded off in truly great style when Lewis was crowned the McLaren BRDC Autosport Award winner for 2010.
Lewis was signed by the Arden team for the 2011 GP3 series and had a good year, complete with a stunning victory in front of a packed Silverstone British Grand Prix crowd and a pole position in Valencia. Lewis achieved three podium finishes and finished 7th overall in the championship. He was also given the opportunity to race in Formula Renault 3.5 as replacement for Daniel Ricciardo, who was on third driver duties for Toro Rosso at the Chinese F1 Grand Prix. In addition, Lewis was nominated for the prestigious FIA Drivers Academy.
In 2012 Lewis was selected to join the Red Bull Junior Team. He not only featured as a regular Red Bull F1 Simulator Driver but also raced the full season in Formula Renault 3.5 for Arden Caterham, the squad having close links to the Red Bull F1 team by way of the teams owners, namely Christian and Garry Horner. Lewis was also assisted by Mark Webber, Red Bull's former F1 driver, who guides all Arden's young drivers.
After a last minute phone call from Team Principal Richard Coleman, in 2013 Lewis was selected to join Bamboo Engineering for their Pre-Season testing in both Spain and Portugal. It enabled Lewis to show both his quality and pace with a top three placing in Barcelona and an overall fastest driver in the second day of testing at Estoril. Lewis subsequently signed for Bamboo Engineering, for their inaugural venture into the GP3 Series, scoring Bamboo's first ever GP3 Series points at Barcelona, a fourth place at the Nurburgring, Germany and an excellent third place podium finish at Monza, Italy.