 He secured voice roles for children's television series and had guest roles in American and British television series, including appearing as Oliver Hide in the medical drama "Casualty", a role which he asked to reprise for two longer stints in 2017 and 2019, respectively.Collett then featured in films "Ethel & Ernest", "Dead in a Week or Your Money Back" and "Dunkirk", before being cast opposite Robert Downey Jr. in the 2020 film "Dolittle" as Tommy Stubbins.Collett has also experienced a career in theatre.