Watch on Soap2day. Mark Horton, a British archaeologist, is investigating King Arthur’s castle. But did it really exist? Camelot, the seat of the court of the legendary King Arthur and Queen Guinevere, where the Knights of the Round Table gathered in the 5th and 6th centuries, could it be a real place, inspired by a Roman-era ruin? Mark Horton travels across Britain to examine medieval texts and post-Roman archaeological sites.