[2] King is also an avid fundraiser for Birmingham Children's Hospital, having raised over £8,500 in 2019 while cycling the North Coast 500.

In February 2015, it was confirmed King would move up to GP2, signing with Racing Engineering, alongside Alexander Rossi, for 2015, where he finished twelfth overall.

King missed the Monaco round due to his participation in the 2019 Indianapolis 500, with Artem Markelov serving as his substitute.

King holds two F2 track records, both set in 2017, at Circuit de Spa-Francorchamps and Autodromo Nazionale di Monza.

[8] He made his debut in a Formula One session when he drove for Manor during free practice at the 2016 United States Grand Prix.

He signed with Jackie Chan DC Racing x Jota for the 1000 Miles of Sebring, the 6th round of the 2018-19 Super Season.

King secured the LMP2 victory in his first endurance race[12] and subsequently finished the season with the team.

King has competed in two rounds of the 2019-20 Super Season with Team LNT Ginetta Cars in the LMP1 class.

[16] King made his debut in Berlin with Mahindra, replacing Nyck de Vries, who missed the event due to a calendar clash with 6 Hours of Spa.