Taylor-Wood, 42, casts leading man, 19, as her husband

It is a rock'n'roll move befitting the woman once known as the "wild child" of the Young British Artists movement.

Sam Taylor-Wood, the conceptual artist and film-maker who separated from the art dealer Jay Jopling last year, is to marry her teenage boyfriend, she declared yesterday.

Taylor-Wood, a 42-year-old with two children, apparently fell for the 19-year-old actor Aaron Johnson shortly after he was cast as the lead for her film Nowhere Boy, which premiered to massive critical acclaim at the close of the London Film Festival this week.

The announcement of the engagement came just hours after the couple were seen together on the red carpet. Johnson received sensational reviews for his emotionally – and erotically – charged depiction of the early life of the Beatles singer John Lennon and his relationship with his mother. The film is an account of Lennon's teenage years in 1950s Liverpool, written by Matt Greenhalgh, the author of the Ian Curtis biopic Control, and it was directed by Taylor-Wood.

The couple's relationship was only brought to public attention in May this year, when they were photographed together at the Cannes Film Festival. A spokeswoman for Taylor-Wood confirmed they were engaged and another spokeswoman said they were both "very happy".

Taylor-Wood and Jopling separated last September after a 10-year marriage, during which they had two daughters. The divorce was said to be amicable and Jopling was seen at the Nowhere Boy premiere along with his current girlfriend, Rachel Barrett.

Jopling, 46, has been linked to women decades younger than himself over the past 12 months, including the singer Lily Allen, 24. Taylor-Wood married Jopling, who owns White Cube Gallery, in 1998. Their marriage was seen, in public at least, as a strong one. Their eldest daughter, Angelica, is 12 and their youngest, Jessie Phoenix, was born in 2006, two years before they separated.

Taylor-Wood, who was one of the most prominent faces of the YBA movement of the 1990s, studied at Goldsmiths College and came to be represented by Jopling alongside Damien Hirst and Tracey Emin. During their marriage, she suffered from both colon cancer and breast cancer.

She was feted by the art world before turning her attention to feature-length film-making: she was nominated for the Turner Prize and exhibited at the Venice Biennale. Her works include a video of the footballer David Beckham sleeping and a self-portrait called Single Breasted Suit with Hare, which was created shortly after her breast cancer diagnosis.

Johnson, for his part, has already established a promising acting career. Nominated by the British Independent Film Awards for his performance in Nowhere Boy, the Buckinghamshire boy is due to play the lead role alongside Nicolas Cage in Matthew Vaughn's action drama Kick Ass next year. He has starred in films including The Greatest, opposite Pierce Brosnan and Susan Sarandon, as well as the teen comedy Angus, Thongs and Perfect Snogging by Gurinder Chadha.