A palace spokesman said Prince Philip would gradually "wind down" his workload after he turned 90 in June.

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NEW: Prince Philip is said to have undergone a procedure for a blocked coronary artery

NEW: He will remain at the hospital for observation, the Press Association reports

Earlier, he complained of chest pains, a Buckingham Palace spokeswoman said

Philip, 90, has been married to Queen Elizabeth II for 64 years

London CNN  — 

Britain’s Prince Philip was treated successfully for a blocked coronary artery on Friday and will remain at the hospital for observation, the Press Association reported, citing a statement from Buckingham Palace.

Earlier in the day, Philip was taken from Sandringham to the cardiothoracic unit at Papworth Hospital in Cambridge after complaining of chest pains, according to a Buckingham Palace spokeswoman.

Tests determined his chest pains were caused by a blocked artery, which was “treated successfully by the minimally invasive procedure of coronary stenting,” the PA reported.

Philip, the husband of Britain’s Queen Elizabeth, is also known as the Duke of Edinburgh. He will stay at the hospital for the “immediate Christmas period” for observation, the agency said.

The royal family traditionally spends Christmas at Sandringham, the private home of four generations of British monarchs.

Philip turned 90 in June, at which point a Buckingham Palace spokesman said the Duke of Edinburgh would gradually “wind down” his workload.

“I reckon I’ve done my bit, I want to enjoy myself now … have less responsibility, less frantic rushing about, less preparation, less trying to think of something to say,” Philip said then, in an interview with the BBC.

He married then-Princess Elizabeth on November 20, 1947, in Westminster Abbey, and has become the longest-serving consort in British history.

Philip has made more than 5,000 public speeches during his working life, according to Buckingham Palace.

CNN’s Max Foster contributed to this report.