Katy Perry shared a beer with a fan at her concert in London last night (27.05.14).

The pop princess enjoyed a pint which came up through the stage with her acoustic guitar during her 'Prismatic World Tour' show at The O2 arena, but after taking a few gulps and repeatedly burping, Katy found a guy in the crowd to give it to along with her ''cooties''.

Before performing 'The One That Got Away', she said: ''I was just expecting my guitar but I have a pint of beer ... I've got to stop (drinking it) otherwise I'll be burping through this song. Someone help me out with this beer. I'm looking for a specific person, the guy who was dragged here by his girlfriend. You sir have this and have my cooties forever.''

Earlier, Katy opened her incredible show with 'Roar' wearing a flashing neon dress and backed by spear-wielding soldiers dabbed in luminous paint.

The concert was split into four sections and after the Prism part, the singer played an Egyptian-themed set during which she rode a huge horse while dressed as Cleopatra for 'Dark Horse'.

She then performed a rock version of ''oldie but goodie'' 'I Kissed A Girl' which saw her two guitarists fly through the air as sparks streamed from their instruments.

Her Cat-Oure section featured a version of 'Hot n Cold' seemingly inspired by the musical 'Cats' with Katy spinning round the impressive prism-shaped stage in a jewel-encrusted pink pussy bodysuit backed by her feline dancers followed up with a rendition of 'International Smile' which merged into a brief cover of Madonna's 'Vogue'.

The 29-year-old star exposed her emotional side during her Acoustic set and alluded to her split from ex-husband Russell Brand as she introduced a moving performance of 'By The Grace of God'.

She told her fans: ''This next song I was a little bit nervous about writing it, because I'm a pop star and pop stars are supposed to be invincible. But I wanted to write it for anyone who thinks they're going through something on they're own. Like, 'He's tweeting and he's not texting me back.' You hear this song and you're not so alone. Remember when you can't get out if bed because things are so hard, just remember Katy Perry - the girl with many hair colours - put one foot forward and got out of bed.''

Her final tracks - dubbed her Hyper Neon section - proved Katy is the queen of bubblegum pop as she had the sell-out crowd on their feet screaming for 'Teenage Dream', 'California Gurls' and latest single 'Birthday' - during which she brought one lucky birthday girl named Hayley on stage to sit on a throne and take a selfie with her idol before the singer then floated off around the arena clutching a bunch of balloons.

Katy - who closed her stunning set with 'Firework' - will play three more shows at The O2 this week; tonight (28.05.14), Friday (30.05.14) and Saturday (31.05.14).

Katy Perry 'Prismatic World Tour' set list:

Prismatic:

'Roar'

'Part of Me'

'Wide Awake'

'This Moment'/ 'Love Me'

Egyptian:

'Dark Horse'

'E.T.'

'Legendary Lovers'

'I Kissed A Girl'

Cat-Oure:

'Hot n Cold'

'International Smile' / 'Vogue'

Acoustic:

'By The Grace of God'

'The One That Got Away'

'Double Rainbow' / 'Ghost'

'Unconditionally'

Throw Back:

'Megamix Dance Party'

'Walking On Air'

'It Takes 2'

'This Is How We Do' / 'Last Friday Night (T.G.I.F.)'

Hyper Neon:

'Teenage Dream'

'California Gurls'

'Birthday'

Encore:

'Firework'