U2 fans that turned out for the band's performance in London last night got a little something extra for the price of their ticket: a surprise appearance from Patti Smith, who joined the group for renditions of "Gloria" and her own "People Have the Power."

As NME notes, the show came in the midst of a six-night stand at the O2 Arena, and marked the second time this week U2 have welcomed a special guest onstage; on Oct. 26, they were joined by Oasis co-founder Noel Gallagher, who chimed in for a performance of "I Still Haven't Found What I'm Looking For" that segued into the Beatles' "All You Need Is Love." You can check out Smith's appearance with U2 above, and watch Gallagher's below.

Promotions for the band's current tour will continue in the weeks to come, with HBO scheduled to air a behind-the-scenes documentary on Nov. 7, followed a week later by a broadcast of the group's Paris show. The concert special will receive a number of repeat airings throughout November; for a list of showtimes, visit HBO's website.

Meanwhile, the group is already making plans to release Songs of Experience, the follow-up to last year's Songs of Innocence. Promising they'll have the record in stores "next year," singer Bono recently revealed that despite the fact they've been on tour — and he himself required extensive surgery after a bike accident — preparations for the new LP are well under way.

Watch U2 Perform With Noel Gallagher

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