In 2016, Mitchell transitioned into sports car racing, joining Ecurie Ecosse in the GT4 class of the British GT Championship.

[4] Claiming two class victories at Snetterton and Donington Park, Mitchell and co-driver Ciaran Haggerty finished third in the GT4 championship.

[5] 2019 saw Mitchell reprise his role in the Barwell Motorsport entry, alongside adding a full-season drive with Prestige Performance in the Lamborghini Super Trofeo North America.

[8] In October, Mitchell defended his Silver Class crown at the 24 Hours of Spa, taking victory for Barwell Motorsport for the second consecutive year.

In British GT, Mitchell and Balfe claimed two race victories, at Snetterton[16] and Donington, en route to a fourth-place championship finish.