His decision was announced in May 2017 even though he did not step down from his duties until August. Prince Phillip was ascended to the throne in 1952 and has since been to 22,219 single working events.
According to a former butler, it was two things that made him retire. Firstly, his deteriorating health at age 95 that can make a simple cold feel like a severe illness. Secondly, the passing away of his dear friend Sir Brian McGrath left him wondering whether he wants to spend his final years working.