The show said: “It is with great sadness that we announce the death of our dear friend and colleague Graham Lay. He will be deeply missed by all the team.”
Fans and experts took to Twitter to express their sadness.
Catherine Southon said: “So sad to hear about dear Graham, a lovely man and always very generous with his knowledge.”
Fellow Antiques Roadshow expert Marc Allum said: “Terribly sad to lose such a lovely colleague. Such a great asset to the show and so stoic over the years. He lived with illness and never moaned at all. Thoughts are with his family.”
Lay, whose knowledge of military history and militaria expertise was much admired, joined the provincial firm of auctioneers King & Chasemore in 1975 as a reception porter. He moved to London in 1978 when Sotheby's took over the firm. He had also worked at Bonhams.
He was a Blue Peter fan and always wore his Blue Peter badge for his Roadshow appearances.