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The 'Wide Awake' singer launched her new film in the UK capital while Lawson and Conor Maynard also attended.
Fresh from launching her 3D documentary in Sydney, Australia the 'Teenage Dream' singer arrived in London this week for the film's UK premiere.
The 'California Gurls' singer avoided the pitfalls of the British weather with a Union Jack umbrella while walking the premiere's specially made pink carpet.
Katy walked the pink carper at the Part Of Me 3D premiere with Union Jack themed eye make-up to show her love for the British public.
The 'I Kissed A Girl' star attended the premiere of her documentary in London's Leicester Square, where she posed for photographers and fans outside the Empire cinema.
The 'E.T.' singer spent a long time meeting and greeting her biggest UK fans before the premiere in Leicester Square this week.
The 'Teenage Dream' singer's film follows her mammoth 2011 'California Dreams' world tour as well as revealing details about Katy's upbringing and private life.
The 'California Gurls' singer happily leant down to let a very young fan plant a kiss on her cheek outside the Empire Cinema in Leicester Square.
The 'Firework' singer has already premiered her 3D concert documentary in both Sydney, Australia and Los Angeles, California before arriving in the UK this week.
'When She Was Mine' stars Lawson walk the pink carpet of Katy's new film launch in London's Leicester Square this week.
The 'Can't Say No' star dressed up in a white shirt and blazer while posing for pictures outside the London premiere.