The Freedom, which allows its recipients to walk sheep over London Bridge, is typically awarded to individuals nominated by corporation councillors.
Mountbatten-Windsor inherited the status as the child of a Freeman and constitutes a legal right.
Though today largely a ceremonial honour the Freedom is still awarded to individuals on a regular basis.
Sir Lenny Henry and Cate Blanchett are among those to have received the honour.
The former prince was stripped of his royal titles, styles and honours by King Charles last year after further details of his relationship with the convicted paedophile Jeffrey Epstein came to light.
In February he was arrested after correspondence in the Epstein Files suggested he may have passed on sensitive trade information, and was released under investigation after spending 11 hours in custody.
He has denied any wrongdoing.
Additional reporting by Winnie Agbonlahor
