Kate Middleton
Kate Middleton, Duchess of Cambridge PA

Kate Middleton is turning 30 on January 9.

Rumours have it that her party planner sister Pippa and brother-in-law Prince Harry are making arrangements for a big bash for the Duchess of Cambridge on the occasion of her first birthday as a member of the royal family.

According to reports, Pippa is planning an Eighties-themed bash this weekend in collaboration with Harry, to mark the decade the Duchess of Cambridge was born in. The event, peppered with cocktails and karaoke, will be "secretly arranged" inviting only very close friends, a Daily Mail report has said.

On his part, the Duke of Cambridge is said to have commissioned an oil portrait of Kate to mark the occasion. A new watch will also form part of William's birthday gift for Kate. And the monarch is planning to present her with a tiara from the royal collection, according to the paper.

Grazia magazine has quoted a royal insider as saying: "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.'"