Cronenberg joked with the crowd assembled at the Odeon Leicester Square: 'The truth is the reason that you might not recognise London in this film is that it was shot in Prague.'
In a nod to the Russian gangster subculture pictured in the film, Cronenberg held up a small bottle of vodka.
Seriously, Cronenberg thanked his UK partners in the project, including BBC Films and Kudos Pictures. 'I'm happy to return to the scene of the crime, to bring the film home,' he said. The film premiered in Toronto and previously opened the San Sebastian Film Festival.
Cronenberg was joined on stage by producers Paul Webster and Robert Lantos, as well as the film's screenwriter Steve Knight. Actors Vincent Cassel and Naomi Watts were in attendance, but leading man Viggo Mortensen is in Santa Fe, New Mexico, shooting a new film for director Ed Harris.
BFI chairman Anthony Minghella pointed out that the opening of the festival wasn't the only reason to celebrate, as the UK government today announced $50m in further support for the BFI archives.
'That's an amazing thing,' Minghella said. 'In these very lean times it's a salute of real confidence from the government for [BFI director] Amanda Nevill and her team.'
He continued: 'This is the first in what I think will be a whole cluster of good news about the BFI going forward.' The director also reiterated plans for the BFI to establish a National Film Theatre, calling the recently refurbished BFI Southbank, the festival's delegate centre, 'a rehearsal room for the new space.'
The festival continues through Nov 1.