IT MAY only be the size of a thumbnail - but what Win-chester University archaeology student Rachel Cruse unearthed has changed forever what is known about the Roman occupation of South-ampton.

About 1,600 years ago, a Roman metalsmith working in what was to become Southampton discarded one of his moulds used for forming ingots of gold.

The piece of pottery lay undisturbed in the soil for more than 1,000 years before it was excavated by the city's heritage chiefs - and then forgotten.

It then lay in a museum store, just another ordinary piece of Roman pottery, until the sharp-eyed student recognised its real value.

Rachel, 19, of Park Road, Chandler's Ford was on her first week of a work placement with Southampton City Council's archaeology unit.

She was cataloguing fragments of a Spanish olive oil jar from the Roman site of Clausentum when she noticed a small, thumb-sized hollow in the piece of pottery.

When she looked at her work under a microscope, Rachel knew she had struck gold.

Tiny droplets of the precious metal were contained in the hollow - proving for the first time that our Roman ancestors in the city had once worked with gold.

Roman finds have been collected at Bitterne Manor for over 200 years - but it is the first evidence of gold working to emerge from the Clausentum site on the banks of the River Itchen.

Dr Andy Russell, Southampton City Council's head archaeologist, told the Daily Echo: "Thanks to Rachel's sharp eyes, another dimension has been added to Clausentum.

"Roman ingot moulds are very rare and this is a marvellous example.

"It would have been used by a goldsmith when melting down scrap and would have held about an ounce of gold.

"That would be worth about £400 in today's values."

Rachel, a former pupil of Taunton's College, Southampton, said that the piece of olive oil jar had been reused by the goldsmith to make his mould.

She added that she planned to specialise in excavating the bones of our long dead ancestors when she finishes her three-year degree.

She said: "It is the first evidence of gold working in Roman Southampton.

"I could not believe it at first. It's amazing to find something like this in my first week."