After a whirlwind three years — during which he’s gone from unknown outsider to TV heart-throb to internet sensation to Oscar nominee and Olivier Award winner, with barely a pause for breath — the Irish actor will shortly ascend to mainstream-movie stardom, stepping into Russell Crowe’s sandals with the lead role in Gladiator 2, Ridley Scott’s sequel to his epic blockbuster. On a sunny day in central London, Mescal reflects on the ‘bananas’ experience of his lightning-fast rise to fame