Downton Abbey cast members Laura Carmichael, Allen Leech and Lily James were not about to disappoint Prince William. At the exclusive charity dinner to celebrate the work of The Royal Marsden, sponsored by fashion designer Ralph Lauren at Windsor Castle, the three Downton stars held court with royalty. Prince William is a fan of the show, even sharing a laugh with Laura, Allen and Lily as they chatted away merrily. Afterwards, the Downton trio headed to Soho's Groucho Club where they partied on well into the late hours. A somewhat disheveled Lily looked a little worse for wear as she headed home after a long, royal night out.