Taylor Swift secretly supported boyfriend Joe Alwyn at the premiere of his new movie, The Favourite on Friday night (28Sep18).

The British actor, 27, stars in the period drama alongside Emma Stone, Rachel Weisz, Olivia Colman and Nicholas Hoult, and the movie kicked off the New York Film Festival on Friday.

While Taylor avoided the red carpet at Lincoln Center’s Alice Tully Hall, she was seen slipping into the theatre through a back door to join her beau.

The couple were later spotted holding hands as they left the film's afterparty at Central Park’s Tavern on the Green.

The Delicate hitmaker stunned in a flowing black and red Amen dress, which she paired with a black trench coat and black Jimmy Choo shoes.

It was a rare outing for the couple, who have kept their relationship tightly under wraps since they began dating in late 2016. In an interview with British Vogue earlier this month, Alwyn briefly spoke out about their romance for the first time.

"I'm aware people want to know about that side of things," he said. "I think we have been successfully very private and that has now sunk in for people... but I really prefer to talk about work."

Another surprise guest in the audience at Friday night's premiere was Jennifer Lawrence, who was there to support her best friend Emma, and ex-boyfriend Nicholas.

When the La La Land star noticed her Oscar-winning BFF in the audience, she began pointing and waving at her, according to E! News.

The Favourite is set to be released in January, 2019.