Philip began feeling unwell on Tuesday, and was admitted to London’s King Edward VII hospital that evening, the palace said in a statement to media on Wednesday.

“The Duke’s admission is a precautionary measure, on the advice of His Royal Highness’s Doctor, after feeling unwell. The Duke is expected to remain in hospital for a few days of observation and rest,” the statement read.

No further details of the prince’s symptoms or illness were provided.

Philip retired from public life in 2017, and health issues have reportedly troubled the Duke in the years since. He was admitted to King Edward VII hospital shortly before Christmas 2019, and spent four days receiving treatment for an unnamed “pre-existing condition.” He received a heart stent in 2011 and had to give up his shooting hobby as a result, and the tabloid media in the UK has regularly speculated that his health is deteriorating.

Throughout the coronavirus pandemic, both Philip and the 94-year-old Queen spent most of their time sequestered in Buckingham Palace or Windsor. Both royals received their vaccinations against the virus last month, with the shots administered by a royal household doctor.