It’s not a bad way to celebrate the rave reviews. Sam Taylor-Wood, the artist and film director, is to marry Aaron Johnson, the actor 23 years her junior, who plays the teenage John Lennon in her acclaimed film.

There was a glint in Taylor-Wood’s eye as she walked down the red carpet with her leading man at the premiere of Nowhere Boy, which closed The Times BFI London Film Festival on Thursday.

A leading member of the Young British Artists movement, Taylor-Wood, 42, split amicably from Jay Jopling, 45, the art dealer, last year.

A Turner Prize nominee in 1997, Taylor-Wood has battled colon cancer and breast cancer, immortalising her recovery in the self-portrait, Single Breasted Suit with Hare, which hangs at the National Portrait Gallery.

She surprised the art world and announced that she would make a feature film charting the relationship between the 15-year-old Lennon, his mother, Julia, and the severe Aunt Mimi who brought up the musician.

She cast as Lennon the relative unknown Johnson, 19, from High Wycombe, who has had television parts and roles in films including The Illusionist and Angus, Thongs and Perfect Snogging.

The director and her teenage star revealed their relationship at the Cannes Film Festival this year. After the triumphant gala screening on Thursday, a spokesman for the couple confirmed their engagement, adding that though they have not set a date for the wedding, they were “very happy”.

Jopling, who still represents his former wife’s art projects, gave the couple his blessing. He attended the screening with his new girlfriend, Rachel Barrett, and his daughter by Taylor-Wood, Angelica, 12.

After his split with Taylor-Wood, Jopling had a brief relationship with Lily Allen, 22.

A student at Goldsmiths College, where Damien Hirst and Jake Chapman trained, Taylor-Wood made some of her most provocative works using video art. One of her most famous was a short film of David Beckham sleeping.

Critics praised the sensitivity of her handling of the triangular relationship at the heart of Nowhere Boy and her grasp of period detail. Johnson has also been hailed as a future star for his portrayal of Lennon.

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