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Sean Biggerstaff’s tribute to Alan Rickman proves just how far the late actor’s impact reached. Biggerstaff held a small role on the first two Harry Potter films, but he and Rickman — who died on Thursday at age 69 — maintained a 20-year friendship.

“I don’t know what I did to deserve a friend like Alan,” Biggerstaff wrote on Twitter. “He looked out for me for 20 years and I loved him. I don’t know what to do now.”

Biggerstaff played Oliver Wood in Harry Potter, and shared a lengthy and personal remembrance of the late actor in a subsequent tweet. The actor explained how he first met Rickman as an 11-year-old, and carried the friendship with him through the Potter films and beyond.

“He’d be on a mad press trip round the world, having just finished a Broadway show and be about to start shooting a film — with several other projects as an actor, director, writer, board member, mentor bubbling away in the background — and if I needed anything he would immediately spend hours of his time helping me,” Biggerstaff wrote. “AND, amazingly, I know of at least a dozen other people who had this same relationship with him. He was our fairy Godfather. He was the whisper in the right ear at the right time. He was the reassuring message when he sensed, always correctly, that we needed it most. He was new head shots or carpets or travel money when times were tough. How he found the time, let alone the will for all this is a mystery to me. He was the most generous, wise, supportive, talented, charismatic, empathetic person I think I’ve ever known.”

Biggerstaff added that the last time he saw Rickman was after the actor, unbeknownst to him, had been in the hospital for an extended period. “He got out that morning… and kept our theatre date. In a strange way I’m glad of that frightening episode, as it made me realize that even he was a mortal of flesh and blood and a certain age and he might not always be there. That evening when we parted, I hugged him and told him I loved him and I’m very glad of that now.”

Biggerstaff isn’t the only one in connection to Harry Potter to pay tribute to Rickman. In addition to fans mourning Rickman at Platform 9 3/4 in London, Daniel Radcliffe, Emma Watson, and the series’ author J.K. Rowling all shared their thoughts on social media Thursday after learning of his death.

“There are no words to express how shocked and devastated I am to hear of Alan Rickman’s death,” Rowling wrote on Twitter. “He was a magnificent actor & a wonderful man.”

Read Biggerstaff’s full tribute to Rickman here.