Director Doug Liman tries to accomplish the impossible.

The 48-year-old filmmaker managed to get permission to have a military helicopter land in London's iconic Trafalgar Square for his latest film 'Edge of Tomorrow' and insists he only managed to pull that off because he was persistent and refused to take 'no' for an answer.

He told The Times 2 supplement: ''It's easy to propose something outrageous in a pre-production meeting like, 'What about landing a military helicopter in Trafalgar Square?

''And the location manager will say, 'That's absolutely impossible. Two weeks before the scene they showed me the helicopter we were allowed to use and I immediately said 'That's not big enough'. And they said, 'It's all we could get, the RAF turned us down'.

''I said, 'Go back and try again'. And they did and eventually the RAF said yes.''

Although film-making doesn't run smoothly Liman insists challenges and ''chaos'' help him better his work.

He added: ''A little bit of chaos around me tends to bring out the best in my work.''