The 75-year-old is starring in AR Gurney's poignant Love Letters with his wife of 56 years, Lydia.

The veteran couple sit throughout the play which is about two lovers' lifelong correspondence.

They have played the roles before in US productions and on a regional tour of the UK in 1997. Heston last appeared in London at the Queen's Theatre in The Caine Mutiny Court Martial in 1985.

Heston says Love Letters is funny and poignant

"It's a very unusual piece. It's a two-hander," says Heston.

"It consists of two people - a man and a woman - sitting side by side at a desk, reading letters they have written to each other starting when they're eight years old until they're in their 60s.

"I know of few pieces that are as funny as this is and at the same time as heartbreaking, it's a marvellous piece of work."

Heston has played his role opposite other actresses in the past, but - unsurprisingly - he says his wife Lydia is the best. "She was born for it," he adds.

It was only at the end of Thursday's opening night, during the curtain call, that the veteran actor looked frail and was seen to stoop.

Cancer battles

Earlier this year, the man who shot to fame in Hollywood epics Ben-Hur and El Cid spoke of his battle against prostrate cancer, but said he was beating it with radiation therapy.

Lydia Clarke Heston fought her own battle against breast cancer several years ago.

Classic scene: The famous chariot race in 1959's Ben-Hur

Love Letters first opened in New York in 1989 and has enjoyed many celebrity casts. They include the original performers, Kathleen Turner and John Rubinstein, to Paul Newman and his wife Joanne Woodward.

The Hestons are the latest Hollywood stars to appear on the London stage.

Nicole Kidman recently drew packed houses to the Blue Room at the Donmar Warehouse, while Kevin Spacey won an Olivier award for his performance in Eugene O'Neil's The Iceman Cometh at the Old Vic.