There may be hundreds of great buys to be had at Bristol's new £500 million, state-of-the-art Cabot Circus shopping complex, but for Simon Cox the real treasures lie beneath the surface.

Over the centuries, the rich history created by generations of Bristolians, has been covered with earth, stones, buildings and Tarmac following the building of Broadmead, part of which was demolished to make way for Cabot. As an archaeologist, Simon's job was to oversee an extensive dig when Cabot was being developed, and to uncover as much of that historical past as possible, as well as record, list or (in some cases) remove any valuable artefacts that were discovered, before the site was covered up once again.

For two years, it was a labour of love for Bristol-born Simon and a team of up to 40 colleagues as they carefully sifted through the remains of ancient buildings, roads, churches, burial sites, homes and people who had called the city home from medieval times up to the 20th century.

Simon explained that anyone who thinks modern archaeology consists of a few devotees turning out for a couple of afternoons a week, taking away a few broken pots and then calling it a day, couldn't be more wrong. In fact, it's a big business, and a vital and mandatory part of any major development. No one is allowed to disturb any part of England's green and pleasant land until the "time detectives" have done their work.

Indeed, archaeology is now a vital part of the planning process, and a necessity before the green light is given to any development project.

Simon says it was his Latin teacher, the late Duncan Stainer at Queen Elizabeth's Hospital school in Clifton, who gave him the inspiration to become an archaeologist.

"He used to show us slides of places like Pompeii and Herculaneum, and I was fascinated," he said. "I took a degree at Cardiff University, and then joined Bristol City Council working from the museum. I then worked on projects all over the city including uncovering medieval and Civil War defences at Temple Quay, and the Redcliffe waterfront at Redcliffe Backs, and the old brewery site next to Bristol Bridge. I had always been interested in the history of Bristol, and I used to listen to my grandfather talk about the Temple parish where he lived.

"Since becoming an archaeologist, I have obviously learned a lot more about the city, although this is a profession where you are learning new things all the time. I now go out and give talks to local interest groups."

From the city council, Simon joined Cotswold Archaeology, based at the old Kemble Air Base, near Cirencester, where he is now head of fieldwork. The company carries out projects nationwide, but as a local lad (and with his knowledge of the city) he was tasked with overseeing the Cabot Circus dig along with project manager Tim Bradley, a colleague from London-based Pre-Construct Archaeology, which worked jointly with Cotswold Archaeology on the project.

"This was by far the biggest job I have ever been involved in," said Simon. "First the developer, Bristol Alliance, made its planning application, and then the city archaeologist, Bob Jones, flagged up the important areas which needed to be looked at before work could begin.

"The Alliance's archaeological consultant, Dr Patrick Ottaway, worked with the city archaeologist and the developers to mitigate the effects of the construction work on what lies beneath the surface, and the Cotswold Archaeology/Pre-Construct Archaeology team was brought in to undertake the fieldwork."

Modern machinery moved huge chunks of roadway, giving the team the necessary access to sift through the remains of 800 years of Bristol life in the commercial heart of the city, which was once the second most important in England.

Where high fashion stores like Harvey Nichols now bring customers from all over the region, locals once worked in small cottage industries ~that involved the dyeing of textiles, tanning and leather manufacture, all of which took place in the area adjacent to Broadweir, from the medieval period onwards.

The archeology team found evidence of these industries, unearthing stone walls of medieval origin, which would have divided the land into narrow properties. The houses which faced Broadweir had backyards, backing on to an old course of the River Frome, where the work was carried out. The river was diverted to form the Castle Moat and now runs alongside Broadweir.

Huge superstores and restaurants now loom over areas which belonged to religious orders, like the area off Penn Street (a secluded square called Quaker Friars) where monastic buildings, once the property of the Dominican Friars, were used by the Quakers from 1670. The area lay just outside the medieval walled town and directly north of the castle, and was granted to the Dominican (Black Friars) between 1227-8.

This was at a time when many other religious orders were establishing their monasteries around the edge of the medieval town. Following the dissolution of the monasteries by Henry VIII in the 16th century, it is thought the friary buildings were converted for residential use before becoming the Quaker Meeting House in 1670. The structure (which was later rebuilt in the 18th century) was, until recently, part of the Bristol Register Office and has now been developed into Raymond Blanc's Brasserie.

"On the site of the friary we found a chapel or aisle attached to the choir of the church, along with steps leading to an altar and some ornate floor tiles," said Simon.

"We also found burial sites both within the friary complex, the Quaker burial ground and beneath the crypt of the Penn Street Tabernacle."

The Penn Street Tabernacle opened in 1753 for the followers of George Whitefield. It was replaced in 1957 by the Whitefield Memorial Tabernacle, in Muller Road, Horfield, now the home of Horfield United Reformed Church.

Simon has worked for Cotswold Archaeology on many past digs in Bristol including 1-2 Redcliff Street, for Hanover Cube on behalf of Scottish Widows, in advance of the construction of a Civil Justice Centre; Bristol Harbourside, where walls were uncovered that probably formed parts of the medieval buildings and gardens around the southern side of the Outer Court of the Abbey; and also remains of the GWR railway yards, built in the early 1900s.

"My job involves liaising between the developer, who is obviously anxious to get on to the site, the local authority, which needs regular updates on what we discover, and eventually producing details of those finds for the general public and other archaeologists," said Simon.

"It involves long hours on sites and at meetings, but the ultimate result is very rewarding. A small display can now be viewed at Bristol Museum and Art Gallery in Queens Road until the end of this year."