The programme describes the Museum as a slice of history in itself, in continuous use since the 13th Century and, once a bishop’s palace, it was where the Bible was first translated into Welsh.
But could it also be home to some mysterious cases of mistaken identity and two lost paintings from the time of Charles II?
Dr Bendor Grosvenor and Emma Dabiri travel to Carmarthenshire to investigate two intriguing portraits of a local nobleman and his wife, the Earl and Countess of Carbery, possibly painted by the great Sir Peter Lely in the 17th century.
Bendor has a hunch that one of the portraits is by another hand. Could the portrait of the countess be a lost work by Mary Beale, Britain’s first commercially successful female artist?
Meanwhile, co-presenter Emma traces how the Earl survived the Civil War, how Mary Beale was written out of the history books, and discovers how the cross-dressing men of the Rebecca Riots stormed Carmarthen.
Carmarthenshire County Council executive board member for culture, sport and tourism Cllr Peter Hughes Griffiths said: “This should be a fascinating programme shedding new light on some of the wealth of treasures at Carmarthenshire County Museum.”
Britain’s Lost Masterpieces will be broadcast at 9pm on Wednesday on BBC4.