Premieres are curious things: sometimes, stars rush past fans and press alike and head straight for the cinema. And sometimes, even when they're running late, they sign autographs for the crowds and do impressions of Samuel L. Jackson.

Tom Hiddleston falls into the latter camp.

Talking on the red carpet at the London Film Festival Gala screening of Only Lovers Left Alive, the actor - famous for playing Loki in Thor and The Avengers - spoke about the appeal of Jim Jarmusch's unique take on the vampire genre.

"I'm either making a film about slavery or I'm not."

That was director Steve McQueen talking at the press conference for 12 Years a Slave at the London Film Festival. Together with lead actor Chiwetel Ejiofor, the pair spoke at length about the brutality on screen and the extent to which they pushed themselves to tell Solomon Northup's true, harrowing, extraordinary story - and tell it honestly.

A lot of talk has surrounded Chiwetel Ejiofor and Michael Fassbender in 12 Years a Slave - and deservedly so. But Steve McQueen's harrowing true drama, which had its UK premiere at the London Film Festival this week, also features another astonishing turn: that of Lupita Nyongo'o.

Playing Patsey, the slave owned by Michael Fassbender's Epps, she is abused, whipped and mistreated horribly on screen. She spoke to me briefly at the London Film Festival premiere about how she came to be involved in the landmark piece of cinema: