He went straight back the following day and found more red enamel pieces – dating to between AD 25 to 75.
Mike, of Milford Haven, Pembrokeshire, said: “I knew the importance of them straight away.
“It was just instinct. I’d read all about chariot burials and just wished it could have been me, so finding this has been a privilege.”
The exact location of his amazing find is being kept secret for a major dig – but is located in south Pembrokeshire.
National Museum Wales said it will now try to buy the treasure items found by Mr Smith.
Adam Gwilt, the museum’s principal curator of prehistoric archaeology, said: “These chariot pieces may have been witness to some of the historical events of the time, as Iron Age peoples defended their ways of life and identities, in the face of an expanding Roman empire.”