Prince Harry's beard has drawn criticism following his appearance at the Remembrance Sunday ceremony in London.
'Prince Harry is letting us all down, ' the serving member told The Mirror. "There's no place for beards in the Queen's cavalry", the source claimed. "He should have shaved it off for such an important day".
A Ministry of Defence spokesperson has since confirmed that, as he is no longer a serving officer, the rules do not apply.
"He is, however, a member of the Royal Family and at times his duties require him to don the uniform of a tied or associated regiment and does so with a beard, as did his great-great-grandfather before him".
Defence Secretary Gavin Williamson said: "Remembrance Sunday is an opportunity for both the nation and our armed forces to remember all those that have given so much in the service of Great Britain". Remembrance Sunday is the Sunday nearest to Armistice Day on November 11, the anniversary of the 1918 signing of the peace treaty that ended fighting in World War I.
British Army rules forbid beards, except for a few circumstances, such as strong religious reasons for retaining facial hair.
According to Forces.net, the only military rank permitted to wear a beard while on official duty - during a parade, for instance - is the Pioneer Sergeant.
All were dressed in dark clothing as they watched from the royal box, with the Queen acknowledging the gathered servicemen and women with a wave.
While he now concentrates on his charity work and other Royal duties, he would be expected to adhere to military regulations when he puts his uniform back on.
Other users defended the prince, saying Britain had more pressing issues to be concerned about.