The former partner of Tilda Swinton has revealed he is the child of an incestuous relationship.

Artist and writer John Byrne has said he is the biological son of his mother, Alice, and his grandfather, Patrick McShane.

Mr Byrne, 77, told The Times he found out the shocking news in 2002 when he and the Oscar award-winning actress were at their home in Tain, northern Scotland.

Artist and former partner of Tilda Swinton (left), John Byrne, (right) has revealed he is the child of an incestuous relationship between his mother and grandfather

Mr Byrne was told the news in 2002 by his cousin Aileen while he was at home with Ms Swinton

His cousin, Aileen Kane, had rung to tell him that her mother, Helen, had died.

'[Helen] told Aileen what my mother had told her, when she was much younger. Aileen asked Tilda, "Do you think I should tell Iain [a family name for Mr Byrne]?" Tilda said, "You’ve got to tell him." She called me in and handed me the phone.'

He said that he and Aileen later met in person and he was told the truth then, and once he found out 'everything fell into place'.

Ms Swinton and Mr Byrne split up in 2005 and he has been in a relationship with lighting designer Jeanine Davies (pictured with John left and right) since 2006

He said: 'My mother was constantly voyaging out to Cardonald [where his grandparents lived]. I once thought she wanted him to go down on his bended knee and beg forgiveness. No. She was in love with her own father, utterly and totally.

'I think he gave me that wonderful mixture of genes with his own daughter, the eldest of the family. That’s what they do in Ireland. I presume it’s what they do in unlettered places and lettered places. It’s traditional, and nobody speaks about it.'

His mother had tragically died while in hospital in the 1980s. She suffered from a mental illness which he believes was a result of the relationship.

Mr Byrne split up with Ms Swinton in 2005. The pair have two children together.

The artist has been with theatrical lighting designer Jeanine Davies since 2006.

He is known for designing the front cover of The Beatles album, The Beatles Ballads, and wrote the 1987 series Tutti Frutti, starring Robbie Coltrane and Emma Thompson.

Several of his paintings hang in the Scottish National Portrait Gallery.