In Sunday night's episode, contributor Charles brought along a letter he had received from Tolkien that he had received aged 14.
Charles had written to the author in runes after translating the runes on the cover of his book, and got a response telling him that his use of the language was "correct and readable".
The letter was on just a single sheet of paper, with the torn envelope it arrived in, and Charles couldn't believe it when the BBC programme's book expert Clive Farahar told him he would value the correspondence at £10,000.
He said: "Good lord. I'm astonished."
Farahar told him: "I think it is the top of Tolkien letters. It’s extremely good. Considering the value of the item. I think it’s worth about £10,000."
However, while it was welcome news, Charles isn't about to cash in the letter any time soon.
Tolkien died in 1973 and the letter is a treasured possession.
The surprised guest said: "I regard it as a family treasure. Since it’s addressed to me and has my name on it, I would not dream of selling it. It’s a sort of My Precious.”
The most valuable item to appear on Antiques Roadshow was in 2008, when an employee of Gateshead Council brought along the final maquette of the Angel of the North that the Antony Gormley sculpture was approved from. It was valued at around £1m.
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