The British actor has been cast as Jace Wayland, a half-man, half-angel who romances Lily Collins in the forthcoming adaptation of the best-selling young adult novel.
And the 23 year old reveals he has embarked on a tough new exercise regime to ensure he is as fit as possible when shooting kicks off.
He tells Britain's Daily Telegraph, "I'm in physical training. I'm drinking lots of protein shakes. I go to the gym and do weights in the morning, in the afternoon I do Krav Maga, a martial art. If you live in a dodgy area like I do (in London), then it could be a handy thing to have."