The monarch appeared to be in good spirits as she arrived at King’s Cross station after traveling from London to start her traditional Christmas holiday at her Sandringham estate in Norfolk, which is about 110 miles north of London.
Carrying her signature handbag and wearing a pink coat with a patterned headscarf, the Queen boarded her First Class carriage this morning just as her husband traveled in the opposite direction.
“The Duke of Edinburgh travelled from Norfolk this morning to the King Edward VII Hospital in London for observation and treatment in relation to a pre-existing condition,” Buckingham Palace said in a statement. “The admission is a precautionary measure, on the advice of His Royal Highness’ Doctor.”
A royal source tells PEOPLE that Prince Philip did not travel by ambulance.
“It was a planned admission, and he walked into the hospital unaided,” the source added.
It’s unclear how long Philip will remain in the hospital — or if he’ll miss Christmas with the family.
Queen Elizabeth’s husband — who retired from his public duties in August 2017 — has been plagued by health issues in recent years. He abruptly cancelled his appearance at the traditional Maundy church service that he was scheduled to attend with the monarch in March 2018. Philip also skipped Easter Sunday services last year ahead of the announcement that he underwent hip replacement surgery.
However, the Duke of Edinburgh has been seen in public multiple times in the past year, often driving his car (despite a scary car accident in January that resulted in him voluntarily giving up his license) or on carriage rides on grounds of Windsor.
He has also been absent from Trooping the Colour celebrations since his retirement. But the royal was in attendance at Prince Harry’s nuptials to Meghan Markle in May 2018. He also attended his granddaughter Princess Eugenie’s royal wedding in October 2018.
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He was also featured in an intimate photo after the birth of great-grandson Archie in May alongside the Queen, Prince Harry, Meghan Markle and Meghan’s mother Doria Ragland.