British royal Catherine, Duchess of Cambridge's sister Pippa Middleton has opened up about her life in the spotlight, insisting she's still struggling to "make sense" of her new-found fame.

Middleton caused a media frenzy during her sibling's wedding to Prince William last year (11) thanks to her shapely posterior - and since then, she has been hounded by the paparazzi around the globe.

Now the notoriously private 29 year old has confessed she's having a hard time dealing with the constant attention.

In her new party planning book, Celebrate: A Year of Festivities for Families and Friends, she writes, "It's a bit startling to achieve global recognition before the age of 30 on account of your sister, your brother-in-law and your bottom.

"One day I might be able to make sense of this. In the meantime I think it's fair to say that it has its upside and its downside... I can assure you that it feels even stranger to me than it probably does to you to have seen so much written about me when I have done so little to paint a picture of myself. "

The book is set to hit stores on 30 October (12).