The revelations last week that Princesses Beatrice and Eugenie have been living rent-free for two decades in grace-and-favour homes in royal palaces have drawn considerable outrage.

A report by the National Audit Office has laid bare some of the cosy deals that working - and non-working - royals have benefited from when it comes to residences.

The rent for Princess Beatrice's London apartment in St James' Palace and Princess Eugenie's cottage within the Kensington Palace grounds is picked up by the Privy Purse - the…