Sam Taylor-Wood says Johnson is 'perfect' as the young John Lennon
Artist and film-maker Sam Taylor-Wood, 42, is to marry her 19-year-old boyfriend Aaron Johnson.
Johnson is the star of Nowhere Boy, Taylor-Wood's first feature film as director, which tells the story of John Lennon's early life.
A spokesman for the Turner-nominated artist said: "Sam and Aaron are engaged and very happy."
The pair were seen this week walking the red carpet of Nowhere Boy's London Film Festival premiere.
Taylor-Wood praised Johnson for his "perfect" portrayal of an adolescent John Lennon.
"When he came for the audition at the beginning I knew he was perfect because he just had the intensity, the focus and the charisma to pull off such an iconic role," she said.
"I saw 300-odd people and he was the only one that stood out."
Taylor-Wood and her first husband Jay Jopling, the art dealer, divorced last year but they remain on good terms.
Following the break-up Jopling had a brief relationship with singer Lily Allen, who is 22 years his junior.