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Professor Dumbledore is ailing.

Richard Harris, best known to millions of young Muggles as the wizened, kind-hearted Hogwarts headmaster Albus Dumbledore, is battling cancer.

The noted Irish thespian has been diagnosed with Hodgkin's disease and is currently hospitalized at London's University College Hospital, where he is undergoing chemotherapy to stem the cancer, his Los Angeles-based agent confirmed on Tuesday.

"He's undergoing tests," Harris' rep tells E! Online.

The 72-year-old Harris was reportedly hospitalized in August after complaining of a severe chest infection. It was then that doctors discovered the Hodgkin's, a cancer which attacks the body's lymph nodes. Nearly 75 percent of adult patients can be cured through chemo and/or radiation treatment.

Harris' spokesperson in London tells the Associated Press that the two-time Oscar nominee has "responded extremely well to treatment and should be released from the clinic soon."

Harris' condition was serious enough to warrant the filmmakers of Harry Potter and the Chamber of Secrets to use a double to complete some of the actor's final scenes.

However, producers discount a report in London's Mirror tabloid claiming they were looking to audition potential replacements for Harris in future Harry Potter installments. In fact, Harris is expected to recuperate in time to don the wizard robes for Harry Potter and the Prisoner of Azkaban, the third film based on author J.K. Rowling's wildly popular fantasy franchise, due to start production in March.

Harris is one of Britain's most acclaimed actors, having starred in such classics as The Guns of Navarone (1961), Mutiny on the Bounty (1962), Red Desert (1964) and the surprise, franchise-launching 1970 hit A Man Called Horse (he later accused Kevin Costner of swiping scenes from the film for Dances with Wolves). Other notable films included This Sporting Life (which earned him a Best Actor Academy Award nomination), the film version of the musical Camelot and Robin and Marian, in which he starred with Sean Connery and Audrey Hepburn.

Harris' career floundered in the '70s and '80s due in part to his increasingly frequent booze binges.

A notorious wild man of the '70s, the actor was once drinking buddies with Peter O'Toole and the late Richard Burton. Harris nearly died from a cocaine overdose in 1978. (According to one newspaper report, Harris has been in intensive care five times over the years and been given last rites twice.) After his O.D., and under doctors' orders, he gave up his hard-living ways and has remained clear and sober since.

Harris has made a comeback over the past decade. He earned a Best Actor Oscar nomination for 1990's The Field and followed with a key supporting role in Clint Eastwood's 1992 western Unforgiven. He played Marcus Aurelius in Gladiator before landing the part of Dumbledore in Harry Potter and the Sorcerer's Stone, the first movie about the adventures of the bespectacled boy magician.

Harris reportedly signed on to play headmaster of Hogwarts after his young granddaughter threatened never to speak to him again if he refused.

Meanwhile, Harry Potter and the Chamber of Secrets hits theaters on November 15.