Doctor Thorne’s Harry Richardson talks horses, heartthrobs and his new pal Tom Hollander

Dressed in jeans, black boots and a cosy jumper, sitting in an airy office in London’s Soho and with a discernible but soft Australian twang, 23-year-old Harry Richardson is talking about horse-riding on the set of Doctor Thorne. “I had only ridden western style, with legs spread and a lax attitude,” he says laughing, an image that doesn’t really say “English gent”. But traditional-style horsemanship in stiff period costume was the order of the day on Julian Fellowes’ adaptation of Anthony Trollope’s nineteenth-century novel about cash-strapped and status-obsessed English aristocratic families. “The horses had been in more films than any of us. They were very professional.” Richardson plays the role of Frank Gresham, a financially troubled heir who’s in love with his beautiful but poor childhood friend Mary Thorne (Stefanie Martini). It is his first major TV gig since graduating from the Western Australian Academy of Performing Arts in 2014. Richardson has English family and he went to primary school here until he was 12, factors that meant Frank’s RP accent was easier to nail than the riding. “I was cheating massively,” he says. At drama school, his tutor would put on Fellowes’ Downton Abbey to help study British accents. Still, going from appearing in one Australian film to a primetime ITV period drama in the coveted Sunday slot is a big step and Richardson, who paid for his own flight to attend the final audition with Martini, is refreshingly self-deprecating. We met before the series aired and he told me that he planned to watch it with his two British-based sisters. I suggest they’ll be proud. “Mocking’s more the word.”

He was learning from some of the period drama pros on the Doctor Thorne set. Fellowes was often on hand to give advice on aristo etiquette. “It’s like having someone from that time period with you – no hands in pockets, never, never, never,” he says, repeating one of the writer's mantras. It helped that Martini was also a newcomer and the pair had a wealth of experienced colleagues to turn to, not least Tom Hollander - “hilarious”, “a hero of mine”- in the titular role, Ian McShane as alcoholic railway tycoon Roger Scatcherd and Rebecca Front as Lady Arabella Gresham, Frank’s scheming mother, desperate for her son to marry well to secure the future of the family seat. Cressida Bonas, Prince Harry's former girlfriend, also appears in her first TV role. Hollander in particular seems to have taken Richardson under his wing, inviting the newcomers to lunch so they could ask as many questions as they wanted. “Both of us were fresh out of drama school, we’d never done something like this with an arc or journey,” he said. Is he worried about Doctor Thorne going up against Hollander’s other project The Night Manager, currently pulling in eight million viewers in the Sunday night slot. “It’s a win, win for Tom.”

With one episode to go, viewers are waiting to see whether Frank will get to marry Mary, or if he will be thwarted by the family need for money. So far, the old-fashioned-feeling but cosily entertaining series has attracted around three million viewers, some of whom have noticed Richardson’s leading-man good looks (he's tall, with the kind of dark wavy hair that actually looks good in a top hat) that could garner comparisons to Aidan “Poldark” Turner. “I don’t think anything can prepare you for that,” he says of heartthrob status. In this series however, he avoided any topless scenes. “I got out lucky,” he laughs. He has now permanently relocated to London and is looking for his next job in the UK, on stage or screen. “It is an exciting time to be a young actor. The possibilities are infinite, there’s no real roof on anything.” Before he heads off into the Soho sunshine, He tells me that evening he’s off to the theatre with Hollander. I sense we’ll be seeing more of them both.

The final episode of Doctor Thorne is on Sunday at 9pm on ITV. It will also be available on DVD and digital download from Monday