This week, Antiques Roadshow is in Yorkshire at the glorious Piece Hall in Halifax, the only surviving 18th-century cloth hall where textiles were once traded. Treasures include a Chinese imperial robe, an opal pig and a stunning sapphire brooch. Eric Knowles marvels at a Lalique bedside clock, saved from the tip, while specialist Lisa Lloyd explores the magic associated with a pair of mysterious 17th-century doors, rescued from a building site. Andy McConnell investigates what might be the oldest glass ever to appear on the programme – but is it genuine? And jewellery specialist John Benjamin has his own mystery to solve with what appears to be the largest sapphire he has ever seen, but which the owner believes to be glass.