A woman who believed she owned a piece of costume jewellery was stunned after discovering it was worth up to £50,000.
Antiques Roadshow presenter Fiona Bruce hosted the popular show from Piece Hall in Halifax - the only surviving 18th-century cloth hall where textiles were once traded.
In tonight's episode, which was a repeat, a woman wanted to know whether a brooch, known as the "big blue blob" among her family was worth anything.
Expert John Benjamin said: "When we were sitting at the table back there, you said to me I've got a brooch that has always been known as the 'big blue blob'.
"And sure enough when you see it sitting there... it is a big blue blob."
Over the years, the woman had received a number of different opinions on the brooch but most confirmed it was a fake and merely a piece of costume jewellery.
She said: "I inherited it from my grandmother, who gave it to my father, who gave it to me to wear on my wedding day, which I did - something blue."
John told her the brooch was made towards the end of the 19th century.
She said some experts had been "quite rude" to her and her husband and were stunned the couple had wanted it valued, telling them it was just costume jewellery and they should take it away as it wasn't worth anything.
But John said: "They were talking absolute rubbish."
He revealed the brooch was "of significant consequence" because the blue stone in the middle is "an absolutely enormous sapphire".
John said: "I think it weighs 25 to 30 carats and in the world of gem stones, that's quite big."
The expert explained the stone originated from Sri Lanka and is mounted in gold, set in silver and surrounded by white diamonds.
John added: "Now I have to be honest with you, I've done this show for so long, I have never seen a sapphire of this size ever brought into the Antiques Roadshow.
"This is a real first time for me."
He said if he were to consign it to auction, he would expect it to bring £40-£50,000.
The woman gasped and put her hands over her mouth in shock, before laughing while onlookers broke out into applause.
She said: "I don't want to swear... blooming heck."
John said: "Blooming heck indeed. it's an absolute beauty, you know, what else can I say about it? It's fabulous. Thank you very much indeed."
*Antiques Roadshow airs on BBC One
