Stoneman won the FIA Formula Two Championship in 2010, securing a test drive with the Williams F1 team at the end of the season.

On the first day of the young drivers test in Abu Dhabi he set the fifth fastest time, just under two seconds slower than pacesetter Daniel Ricciardo.

[3] In 2011 Stoneman had been planning to progress to the Formula Renault 3.5 series, joining fellow young driver tester Ricciardo at ISR Racing,[4] but he was forced to skip the season after he was diagnosed with testicular cancer.

Following Manor's folding four races before season's ending, Stoneman switched to Koiranen GP replacing Carmen Jordá.

In 2015, Stoneman moved to the Formula Renault 3.5 Series with DAMS having picked up the backing of the Red Bull Junior Team.

In addition to competing in Indy Lights, Stoneman tested an Andretti Dallara IR12 Indycar in August of that year.