This is the surprising reason why Bradley Cooper performed at Glastonbury

And on the Pyramid stage no less...

Glastonbury 2017 came to a close last night, with the festival's headliners ranging from Ed Sheeran and Foo Fighters to Katy Perry and Radiohead. Even Labour leader Jeremy Corbyn took to the stage, talking politics and being serenaded by a 100,000-strong crowd singing 'Oh Jeremy Corbyn'.

The most surprising Glastonbury appearance however, came from 42-year-old Hollywood actor, Bradley Cooper, who took the audience by surprise on Saturday by walking onto the Pyramid stage ahead of Kris Kristofferson's set, holding a guitar.

Having welcomed his baby daughter, Lea De Seine, with partner Irina Shayk in March, Bradley has been keeping a relatively low profile, so the Glastonbury Pyramid stage is quite literally the last place we'd expect him to rock up - especially considering no one knew he was musical.

As the actor took to the iconic stage, sporting long hair and a guitar, festival-goers were surprised, with some undoubtedly wondering whether Bradley had changed career path and had formed an indie band.

It turns out, that's not the case, with Bradley actually appearing on stage on Saturday to film a scene for his upcoming film, A Star is Born.

The American musical drama is set for release in 2018, starring Bradley and Lady Gaga, who both appeared at Coachella to shoot similar scenes earlier this year.

'You guys were awesome', he announced to the crowd as he left the stage. 'That was great - it's my sheer pleasure to introduce Kris Kristofferson.'

And it wasn't straight back to work for Bradley after his performance, with the actor choosing to stick around and soak up the festival vibes, even managing to surprise one unsuspecting fan by photobombing his selfie with Brad Pitt.

So essentially, Bradley Cooper won Glastonbury.