Roger Daltrey joked that his knees were sore after 24 years of begging bands to play his cancer charity shows free of charge.

The Who singer began working with the U.K.’s Teenage Cancer Trust in 2000, arranging annual performances at London’s Royal Albert Hall. In a recent interview with the Metro, he said he’d encountered unforgettable people among the patients the charity helped.

“There's quite a few who will stay with me forever – I could never forget them and the letters and cards really mean a lot,” Daltrey said. “I’ve kept them all.”

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The 79-year-old continued: “I’m some old fart of a rock singer and this has given me a purpose. I’m not very good at doing nothing and I’m looking towards the end of a singing career. So this has been something I’m so proud of.”

He added that he and bandmate Pete Townshend were proud of having founded Teen Cancer America in 2012, saying: “We’re getting the chance to get together a lot of data that will really help the science one day.”

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This year’s run at the Albert Hall is Daltrey’s last in the position of curator. Running from March 18 to 24, the schedule includes Robert Plant, Eddie Vedder, Noel Gallagher, the Who and others, with tickets on sale starting Jan. 12.

“Gosh, it was tough at the start because I was determined bands should want to do this for free,” Daltrey said, “and it’s not easy getting big names to actually block out their time. My knees are now so sore from 24 years of begging!”

He continued: “When I see someone famous, I go straight over and ask them to play a gig – and I’m sure they’ll see me now and run away! But not one of the bands has ever come off the stage without saying, ‘What a fantastic experience.’”

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Gallery Credit: Michael Gallucci