UPDATE: Prince Philip left King Edward VII's Hospital on Tuesday.
"The Duke of Edinburgh has today left hospital after being discharged by his Doctor and is now back at Sandringham," the Palace stated. "His Royal Highness would like to thank everyone who sent their good wishes."
Queen Elizabeth is already in Sandringham for her annual Christmas festivities.
The duke traveled from Norfolk to the London-based hospital last week for "observation and treatment in relation to a pre-exiting condition."
"The admission is a precautionary measure, on the advice of His Royal Highness' Doctor," the Palace stated in regard to the planned visit at the time.
Prince Philip has been hospitalized.
On Friday morning, the 98-year-old Duke of Edinburgh traveled from Norfolk to the King Edward VII's Hospital in London for "observation and treatment in relation to a pre-existing condition," Buckingham Palace confirmed in a statement via NBC News. "The admission is a precautionary measure, on the advice of His Royal Highness' Doctor," the palace noted.
Per Buckingham Palace, via NBC News, he walked into the hospital for the planned visit and is estimated to be there for "a few days." Meanwhile, Queen Elizabeth II has remained in Sandringham and her plans have not changed. She traditionally is seen on Christmas Day, when she attends church in Sandringham with the rest of the royal family.
Since retiring from royal duties in May 2017, the duke has retreated from the spotlight save for the occasional appearance, including in October 2018 at Princess Eugenie's wedding. Prince Philip was most recently spotted at Balmoral Castle in August.
As news of Philip's hospitalization broke on Friday, the Queen was photographed arriving at King's Lynn railway station, after taking the train from London King's Cross, marking the start of her Christmas break at Sandringham House.
While he and the queen recently reached their 72nd wedding anniversary, no details were shared on how they celebrated.
At the start of this year in January, Prince Philip was involved in a car accident, but went uninjured. The following month, he voluntarily surrendered his driver's license. In June, he celebrated his 98th birthday.
Get well soon, Prince Philip!
(E! and NBC are both part of the NBCUniversal family.)
(This story was originally published Friday, December 20 at 6:43 a.m. PT).