According to The Daily Mail, invitations have already been sent out for the private bash, which will be held in the State Rooms at Buckingham Palace, on November 14 – the prince’s actual birthday.
While details are being kept closely under wraps by the royal family, guests will include the families of the Prince of Wales and Duchess of Cornwall – including Princes Harry and William and Duchesses Kate and Meghan.
Festivities to mark the milestone occasion began earlier this summer, when Charles threw a garden party at Buckingham Palace for his staff and to celebrate the work of his charities.
It has also been announced that ITV will broadcast a special TV magic show in his honour.
Charles also attended the GQ Awards in London last week, to receive the Editor’s Lifetime Achievement Award for Services to Philanthropy. The prince – who in April 2011 became the longest-serving heir apparent in British history – also features on the front cover of the men’s monthly magazine October issue.