Alex began his single-seater career in Formula Renault UK, dominating the 2011 championship with a record 12 wins from 20 race starts. He was subsequently named British Club Driver of the Year at the 2011 Autosport Awards.
Alex moved up to British F3 the following year and finished fourth before progressing to the prestigious FIA European F3 Championship in 2013 where he claimed third in the standings as the highest placed rookie. Alex ended the season with a dominant victory in the coveted Macau F3 Grand Prix.
In 2014, Alex wrapped up the GP3 title with a record points margin, also becoming the first Englishman to claim this title.
As well as his Development Driver duties for Williams Martini Racing in 2016, Alex also competed in GP2 Series for the championship-winning DAMS racing team for a second year.
At the end of 2017 Alex joined DS Virgin Racing as a driver in the FIA Formula E Championship and also became an Aston Martin Racing factory driver in their World Endurance Championship programme. He continued in Formula E with Jaguar Racing for part of the 2018/19 season while continuing his sportscar racing in WEC.