Red Bull team principal Christian Horner says Max Verstappen is free to let off steam in other motorsport series, but reaffirmed that the Dutchman’s “focus has to be” on Formula 1 following a secret test at the Nurburgring last week.

Verstappen’s future in F1 has been questioned this season following a challenging start to Red Bull ’s campaign. The Dutchman has been linked with Mercedes and Aston Martin, but has previously stated his desire to compete in other racing series during the prime of his career.