Actress Keira Knightley failed to attend Thursday's premiere of a film written and directed by her boyfriend Rupert Friend because she was unwell.

Asked what was wrong with Keira - who stars in the short film - Rupert said she was feeling "under the weather".

Speaking ahead of the screening of Steve at Southbank's National Film Theatre in London, he described working with Keira as "amazing".

He said she was a "brilliant person and a brilliant actor" and he "couldn't have had anyone better" to work with on his directorial debut.

Rupert, who acted alongside Keira in the 2005 film Pride and Prejudice, said he had not planned on working with her on the project but he would jump at the chance again.

The 16-minute short also stars Colin Firth as the eponymous character Steve, along with Friend's actor friend Tom Mison.

The film, which Rupert described as a "story about a man who came to tea", was shot over three-and-a-half days in Hackney, north London, in May.

He said the film came about after he wrote a short story and mentioned it to Colin.

"He said as a joke, 'If you ever decide to make it into a film, I'd love to play Steve'. So I just thought, 'there's a challenge'," Rupert said.