Cirencester Park comes with a warning: overstay past five o'clock and the gates lock behind you. This private estate of the Earl of Bathurst hides behind a yew hedge the Guinness Book of World Records calls the world's tallest, standing 43 feet high and 510 feet long. Planted in 1720, it takes two men twelve days to trim each August, and the clippings contain paclitaxel, used in chemotherapy drugs.

Its fourteen and a half thousand acres were laid out in the early 1700s by the first Earl Bathurst with his friend Alexander Pope, the poet who funded his career translating Homer's Iliad before turning to landscape design. Their work survives in riding avenues and follies like King Alfred's Hall.

VoiceMap's Cirencester tour, guided by Blue Badge guide Owen Bowles, traces how a market town that once rivalled Roman London still guards its grandest garden.