Mark Smith was left bowled over by a selection of British war medals during the Roadshow's journey to Alexandra Gardens in Cardiff last year.
In an instalment that will air once again on Sunday evening, the episode saw host Fiona Bruce accompany Smith and the other team of experts to the Welsh capital to see what treasures they could unearth.
Smith was on hand to lend his expertise to the war medals, and within moments it was clear to see the expert was excited by the collection in front of him.
In scenes that will be repeated tonight, Smith said to the owner: "You have an incredible collection of these really quite iconic rare medals. Where did you get them from?"
BBC Antiques Roadshow: Alexandra Gardens guest brought in a collection of medals
BBC
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"My dad. My dad passed away and he left them to me," the guest replied.
The owner went on to note that he had a "massive" collection thanks to the fact his dad had been collecting since "he was a young fella".
Smith chipped in: "Well he had a very good eye, trust me. If we look at this one, for example, it has the Battle of Waterloo on the back and it has the word 'Wellington'."
As the camera zoomed in on the medal, he continued: "Now, this is really the first medal that the British forces ever gave to anybody.
BBC Antiques Roadshow: Mark Smith was the expert on hand to evaluate the items
BBC
"Before that, we gave out things that looked like coins, they didn't have your name on, you couldn't wear it, you put it in your pocket.
"But at the end of the Battle of Waterloo, this medal was institued to be given to every soldier and instead of it being made in different metals for different ranks... on this particular occasion, they should all be exactly the same because we all did exactly the same job."
Smith concluded his history lesson: "So Lord Wellington got one of these and so did to the 10-year-old drummer boys who were on the battlefield that day."
As the Antiques Roadshow expert continued to peruse over the over medals on offer, he pointed out the names, including a "Military General Service Medal" first coined by Queen Victoria.
"It's quite a rare medal," Smith noted before he turned his attention to a "King's German Legion" medal.
Summarising, Smith said: "They really are quite spectacular. You don't see Waterloo medals like that unless you go to a regiment or a museum really."
Before long, the conversation turned to the value of the items, with the owner admitting he "hadn't a clue" about how much they'd fetch.
This prompted Smith to joke he'd offer £25 as laughter rippled among the surrounding crowd - although their chuckles turned to gasps when he revealed the true value.
BBC Antiques Roadshow: Mark Smith and the owner discuss the medals' value
BBC
"£12,000," Smith emphatically told the medals' owner, which sparked a shocked reply.
"Never!" he replied, but before he could get carried away, the guest explained exactly why they wouldn't be going to a new owner.
He told Smith: "I wouldn't part with them, Mark. My grandson will have them. Perhaps they'll be worth £40,000 one day, he's only four now. It might pay for a car one day."
"They are special," Smith beamed. "Thank you very much."
