06/01/2012 07:42 GMT

Kate Middleton's 30th Birthday Bash To Be 'Low Key Affair'

Bets are on for what kind of celebration Kate Middleton will have to mark turning 30, but the Duchess of Cambridge is to celebrate her 30th birthday with a "low-key and private" event.

Kate turns 30 on Monday but apparently she will not be having a lavish party.

She reaches the milestone after a momentous year that has seen her marry royalty, embark on her first official overseas tour and take on several patronages.

There had been reports that Prince Harry was planning a big bash for his sister-in-law.

But a St James's Palace spokesman gave a brief statement saying: "Whatever is planned will be low-key and private."

It is thought Kate will spend her birthday with William and close family and friends.

The day before her celebrations the Duke and Duchess will attend the UK premiere of War Horse in London's Leicester Square, where the world's media will be waiting.

William, an RAF search and rescue helicopter co-pilot, is rostered to work next week from his base at RAF Valley in Anglesey.

Turning 30 will cap a life-changing 12 months for the new royal, who married her fiance on April 29 last year in a glittering Westminster Abbey ceremony in front of a television audience of billions.

Earlier this week it was announced the duchess had agreed to support four organisations, two as patron - Action on Addiction and the National Portrait Gallery - and East Anglia's Children's Hospices and The Art Room as royal patron.

The duchess will also become a volunteer with the Scout Association, joining activities privately with groups in north Wales and other areas in a post known as an occasional helper.