As Justin Bieber’s year-long descent into self-parody has proven, it can be hard for a young star to stay grounded when everyone keeps insisting you’re wonderful. Although 18-year-old actor Alex Lawther hasn’t quite achieved the same level of exposure (a fate he will hopefully be spared), the humbleness he shows in spite of his talent is nonetheless extraordinarily endearing.

Consider, for instance, that his debut in David Hare’s South Downs saw him last year nominated for What’s On Stage’s Newcomer of the Year Award and told by Dame Maggie Smith that “most of us spend our lives trying to do what you’ve achieved”.

By autumn, he was one of the youngest names included in Tatler’s Little Black Book – a list of the most eligible men and women in town that many boys his age would pay to be in. Yet the praise that truly sends his cheeks flushing comes halfway through our interview when he talks of the figures he aspires to.

“I’ve had the luck of working with some really wonderful actors,” Lawther explains. “I did South Downs with Nicholas Farrell who was so great and a sort of mentor for us younger actors.

“On a less professional level, I love Sally Hawkins and did a film with her last year, but we didn’t have any scenes together which was heartbreaking. I also really adore the work of Ben Whishaw – I think he’s brilliant.”

So Lawther must be thrilled then, I say, to have been called the next Ben Whishaw by the Evening Standard?

His voice changes into a bashful splutter; he hasn’t read the article. “Oh, well that’s not fair! Ben Whishaw’s still being amazing – he’s still exploding all over the world. That’s just… well, it’s hyperbole, isn’t it?”

The young actor’s new Hampstead Theatre show, The Glass Supper, will see him line up against Michelle Collins and Michael Begley in a story by BAFTA nominee Martyn Hesford.

The story sees couple Marcus and Colin escape the madness of London to live in the peaceful countryside, but the appearance of Stephen, accompanied by his youthful boyfriend Jamie (Lawther) and friend Wendy (Collins) soon causes renewed mayhem.

Asked if he shares any similarities with his character, Lawther says: “Jamie’s very far removed from my impression of myself, but he has essences that all young people kind of share. He has an interest in life – everything’s new and exciting for the first time – and he likes to explore the power that comes from being young in a group of older people.”

Born and raised in Hampshire, Lawther knew from a young age that he wanted to be an actor and puts this partly down to being the youngest of three siblings: “No one wants to play with you because you’re the little one, so you have to make up your own games.”

Appreciate

The son of two lawyers, acting was an unknown path, so he joined several local drama groups and the National Youth Theatre, before receiving his break auditioning for South Downs at the age of 16. The play’s initial run proved a success in Chichester and subsequently it moved down to the Harold Pinter Theatre in London to great acclaim.

In addition to The Glass Supper, audiences will soon be able to see Lawther alongside Benedict Cumberbatch and Keira Knightly in the upcoming biopic of Alan Turing, The Imitation Game. “Benedict’s so generous,” the teenager says. “Maybe there are some actors who wouldn’t sit a newcomer down and ask for their thoughts, but he did and I really appreciated that.”

The best thing about being young and employed in London, he adds, is that he has enough disposable income to spend on a constant stream of books, theatre and cinema tickets. He should make the most of the spare time – it’s evaporating with every day he gets older.

Alex Lawther stars in The Glass Supper at Hampstead Theatre, until July 26. Visit hampsteadtheatre.com/whats-on/2014/the-glass-supper/.