IT was always understood a silver cup presented to Penryn in the 15th century was a valuable gift to be treasured.
But the town's mayor was visibly shocked on national TV as an Antiques Roadshow expert told her the "magnificent and spectacular" item was worth up to three times the amount it was insured for.
Collective gasps greeted Alastair Dickenson's revelation to Penryn's mayor Gill Grant that the Lady Jane Killigrew Loving Cup was worth between £100,000 and £150,000.
Penryn Town Council has it insured for £40,000 to 50,000 and will now have to consider increasing this figure.
Mrs Grant said: "It wasn't so much about what it was worth, but about the fact so many people could see it.
"It was very nice to hear it was worth that, but I couldn't wait to get it back into the vault."
Filming took place in September at Events Square in Falmouth, and details of the valuation were kept secret until Sunday's broadcast of the first of two episodes. The second will be on BBC One this Sunday at 8pm.
Penryn town clerk Michelle Davey said: "It was both a shock and a pleasant surprise to find out its real value."
As Mrs Grant told Mr Dickenson and a nationwide audience, the cup, also known as a standing cup, was a gift from Lady Jane to the town which gave her refuge when she ran away from her husband Sir John in Falmouth.
"She stayed with us for about 20 years and when she got her divorce, she bought this cup and presented it to the town and we've had it since 1633," she said.
Mr Dickenson said: "I've seen a few standing cups in my time, but I've never seen anything quite as impressive and magnificent as this.
"It is something quite spectacular."
Miss Davey said: "Although the cup has been highly valued, it's irreplaceable, so any insurance cover would be compensation rather than to pay for replacement.
"We need to carefully consider whether it's worth the extra cost of insurance, given that it's kept in a highly secure location, and would only be likely to be worth its silver value to anyone else."
Other surprises included a chalk drawing by John Singer Sargent (1856-1925) of a member of the public's great- great-aunt Pamela, insured for £10,000 but valued at £30,000 to £50,000.
Expert Dendy Easton said: "I can hardly believe what I'm seeing. It's a rare picture, absolutely stunning and most collectable."
The granddaughter of entertainer Harry Champion (1865-1942) was also shocked when her memorabilia was valued at £5,000 or more.