Antiques Roadshow: Ashton Court 1

Fiona Bruce and the team visit Ashton Court in Bristol, where they examine a piece of street art by Banksy in a local doorway. Expert Rupert Maas reveals the difficulty of valuing graffiti by an artist whose identity is a closely guarded secret. Other finds include a 19th-century automaton that can smoke a cigarette, a nautilus shell engraved with a picture of the city's suspension bridge, a globe clock that provides a surprise to its owner and a posset pot that may have origins closer to home than expected