Pippa Middleton says "it's been a crazy couple of years" since the royal wedding.

Prince William's sister-in-law has been speaking at the launch of her debut book in London on Thursday.

The 29-year-old, whose bottom became one of the most infamous parts of her sister Kate's wedding to William in 2010, said: "It's been a crazy couple of years since my sister's wedding but it's had its upsides and downsides and I just feel really fortunate to be able to build a career as a writer."

Pippa's first book, Celebration: A Year of British Festivities from Families and Friends, is a party planning book but also talks about what it is like to have a royal brother-in-law and a famous behind.

It is widely reported that she was paid £400,000 for the 416-page glossy hardback.