Donovan joined Robert Plant onstage at the Wexford Spiegeltent Festival in Ireland, where they performed Donovan's "Season of the Witch."

The seasonally appropriate song has often appeared in Plant's sets over the past two decades. Most recently, he performed the song on Halloween night at his concert in Dublin. Donovan's appearance, however, marked the first time Plant performed the classic song with its writer.

You can watch fan-filmed footage of their performance below.

In a Facebook post, Donovan described the performance as "historic," noting that the audience "exploded" when he and Plant appeared together. He also implied that the experience may have inspired him to get back to playing live: "It gave me a buzz to perform live again. ... Shall we?" You can see photos from the event in Donovan's Facebook post.

Plant has also covered Donovan's 1966 song "Hey Gyp (Dig the Slowness)" at his concerts. 

The former Led Zeppelin singer is currently finishing up a tour of the U.K. with his band Saving Grace, which includes singer Suzi Dian, guitarists Tony Kelsey and Matt Worley, and percussionist Oli Jefferson. At a show earlier this year (which coincidentally included "Season of the Witch"), Plant commented on the band's relatively low profile. "We are working a new process of fame and acquisition of wealth and treasure by not putting any records out, not selling any T-shirts, not doing a fucking thing, just keep playing," he said.

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