U2 Were Joined by a 'Regal' Guest in New York Last Night

Lady Gaga is the latest guest performer to join U2 on stage during their 'Innocence + Experience' North American tour.

So far, they've had a jam with a U2 tribute act, a random fan and Jimmy Fallon and The Roots - and last night it was the turn of Lady Gaga, who joined the band to play piano and sing on 'Ordinary Love' - the song they wrote for the Nelson Mandela biopic 'Mandela: Long Walk to Freedom' in 2013.

U2 are in the midst of 8 sold-out nights at New York's Madison Square Garden.

Watch Gaga and the band's performance below: