Pippa Middleton and Prince Harry are reportedly planning a big private 30th birthday party for the Duchess of Cambridge, Kate Middleton.

According to Grazia, the pair are planning an Eighties-themed event, complete with cocktails and karaoke, in a secret London location for “close family and friends”.

The party is reportedly planned for this weekend, ahead of Middleton’s birthday on Monday, January 9.

Grazia's royal source said: “In many ways, this is going to be Kate's last chance to let go like she did back in the old days when she and William first met.

“The party has been months in the planning. Pippa and Harry have been in the thick of it, and have recruited a bunch of friends to help.

“The guests have been sent ‘save the date’ cards, and told that it will probably be in London.

“Given the people organising it, you can be sure it will be brilliant.”