Their romance has gone from strength since sparks first flew back in May 2017.

Taylor Swift was every inch the supportive girlfriend on Monday night as she slipped into the Mary Queen of Scots London premiere to support actor beau Joe Alwyn.

Taylor is said to have slipped in through a side door of Cineworld Leicester Square to avoid the red carpet, with her cover rumbled when a movie co-star shared a photo of her at the after-party.

Scottish actress Izuka Hoyle, who plays courtier Mary Seton, shared a snap of herself chatting to the songstress on Instagram.

A source told The Sun a modest Taylor wanted the focus to be on her British boyfriend, 27, on the night.

They said: 'Taylor didn't want to draw attention to herself because it was really Joe's night.

'But she did want to support him and knew he would appreciate her being there, so she took steps to try and prevent anyone knowing she was there.'

The pair have been dating since May 2017, although have only been spotted together a handful of times.

In September 2018, Joe spoke about his low-key yet blossoming romance with Taylor.

'I think we have been successfully very private and that has now sunk in for people … but I really prefer to talk about work,' he told British Vogue in a new interview for the magazine's October issue.

The film is set to hit the big screen on January 18, and was released in the United States on 7 December.