The actress, who is 39, is a patron of the Children’s Surgery Foundation which helps pay for equipment for children in hospitals.
She is the wife of Lord Frederick Windsor, who is the son of the Queen’s first cousin Prince Michael of Kent.
They married in Hampton Court Palace in September 2009 and have two daughters – Maud, six, and Isabella, four.
The royal will only be starring in one of the four episodes, according to IMDb.
Her other recent TV roles include Sanditon, Trust, Death in Paradise and Robin Hood.
source: express.co.uk