Florence Welch of Florence and the Machine joined rock icons the Rolling Stones onstage last night (Nov. 29) at the second of the band's two gigs at the O2 Arena in London, where the were celebrating 50 years of rocking and rolling. The old guard collided with the new in this hellfire performance. It was certainly a marriage of generations of English musicians.

Welch belted out the Stones' classic 'Gimme Shelter' with the band like she was a veteran member -- and like she had done so a billion times before.

She and frontman Mick Jagger had killer chemistry, dancing back and forth while facing one another. No wonder Welch is one of her home country's newest treasures. That voice is astonishing. And she looked her usual ravishing redhead self in a maroon velvet suit, which is something ol' Mick himself might have rocked back in the day. Check out the fan-filmed footage below.

Watch Florence Welch Perform 'Gimme Shelter' With the Rolling Stones