The first half of the module was shot at Cressing Temple, a medieval moated farmstead in Essex, which is worth a visit. The two 13th century barns, built by the Knights Templar, are truly impressive. And there's a charming 16th century 'paradise garden'.
The rest of the story was shot in London, at the Tower of London and Smithfield Meat Market.
(If you're anywhere near Smithfield, pop into St Bartholemew's Church - without question the finest Norman church in London).