Complex sentence: Cameron's great-great-grandmother was Lady Ida Matilda Alice Feilding, whose father was the 7th Earl of Denbigh GCH PC, a Royal courtier and Gentleman of the Bedchamber.
Split into simpler sentences: Cameron's great-great-grandmother was Lady Ida Matilda Alice Feilding. His great-great-great-grandfather was William Feilding, 7th Earl of Denbigh, GCH, PC, a courtier and Gentleman of the Bedchamber.