Educated at Berkhamsted School, Bly is also a lecturer, public speaker, restorer, valuer, fund raiser, editor and columnist.

He was the presenter of the TV series, Looking At Antiques (1971-1972), had his own show for Anglia TV Heirloom (1975-1992), fronted BBC Crimewatch Aladdin's Cave (1984-1989), BBC2's Heirs and Graces (1989-1990), and was Furniture Specialist on the BBC's Antiques Roadshow (1979-2018)[1] and BBC4 Secret Knowledge (2013).

His own production company, Posh Films with Lady Victoria Leatham, was responsible for the two-part TV programme Treasure Houses of Britain.

He has appeared on the BBC1 chat show Wogan in the late 1980s, and on Children in Need, playing a pair of antique silver spoons as musical instruments.

Bly is a Liveryman of the Goldsmiths' Company 1989, Honorary Citizen of New Orleans, Kentucky Squire, and a past-Chairman of the British Antique Dealers' Association.