The 96-year-old Duke of Edinburgh was meant to attend the Colonel Grenadier Guards ceremony at Windsor Castle on Thursday alongside the Queen but cancelled at the last minute due to health concerns.
The Daily Mail reports that the senior royal was "feeling under the weather". And while the Duke’s condition isn’t believed to be serious, his doctors are said to be exercising extreme caution in regards to his health.
Prince Philip has not been seen publicly since attending a church service after New Years, and he officially retired from public life last August.
This article originally appeared on New Idea.