08/08/2013 03:06 BST | Updated 08/08/2013 08:12 BST

Bedlam Burial Site Uncovered By Crossrail Excavations Finds Skeletons And Roman Treasures

If you ever walked down the London road linking Blomfield Street to Liverpool Street before 2011 it may perturb you to know you were walking on top of thousands of bodies.

Sometimes as little as 60cm below the road surface is the resting place of those buried in the grounds of Europe's first mental asylum - Bethlehem 'Bedlam' Hospital.

Since 2011 the site has been excavated as part of the massive Crossrail project and archaeologists are continuing to make discoveries that shed light on London's extensive past.

A plan of the original Bethlehem hospital. It has been rebuilt twice in different London locations since.

As well as the burial ground which dates from the late 16th century, the remains of a Roman road that once linked the capital to the cities of Lincoln and York has been discovered.

Evidence of what once walked these roads comes from the large number of Roman horseshoes found in the area.

A Roman horseshoe

Most of the newer archaeological material found in Liverpool Street is related to the Bedlam burial grounds, including the first piece of gold discovered during the project.

This is a tiny Venetian coin from 1501-1520. A hole in the top indicates someone of some wealth had used it as a decorative sequin.

The gold Venetian coin

How it ended up in the poor end of 1600s east London is a mystery. Archaeologists have theorised that it was perhaps accidentally thrown out in rubbish or fell off as a high society Londoner passed by in a horse and carriage.

Gold however, can't compete with skulls and bones for sheer intrigue. And Bedlam burial ground has a lot of them.

A skull uncovered on Wednesday

In a space little bigger than a football field, the archaeology team are expecting to find around 3,000.

As Nicholas Elsdon of the Museum of London says, that's "three or four a cubic metre".

The need for space arose in the 16th century when the plague sweeping across Europe overwhelmed the capacity of the traditional graveyards.

He added: "This is one of the densest burial grounds we have excavated in London.

"It's an overflow burial ground when the parish churches just couldn't cope in the city and so they bought a piece of land from Bedlam hospital just behind us and set out this new burial ground.

"They just kept putting more and more people in. It was absolutely chock-a-block."

One of the archaeologists digs around the jumble of bones

Founded in 1330, the Bedlam hospital stood in this location until it was replaced by a more modern building in Moorfield in 1676 but the burial site was used for around another 40 years and was the first in London not to be attached to a parish church.

Many of those buried here would have been patients at the notorious hospital whose name has since become a byword for chaos.

Jay Carver is the lead archaeologist on the entire Crossrail project and relishes being able to excavate cemeteries as "you get contact with individuals".

It's feasible a present-day Londoner could trace their relatives back to the 16th, 17th or 18th centuries, one of whom could be lying in Bedlam burial ground.

Carver says: "One of the things that is exciting is to look at the biographical details of the people in these graveyards and really try and get an idea of their lives."

The conditions of the site mean this is extremely difficult.

Carver says: "The individuals are generally not able to be identified; all the coffins are pretty much rotted. We have found one or two headstones at least one of which is readable.

"So in one case at least we can link at least a name to a burial archive."

This is actually a Roman door key

Although Christian tradition dictated people were laid to rest with no burial offerings, one poignant find was the body of a girl of around 12 with beads around her neck.

Elsdon says: "Someone was upset enough about their child's death to bury them with jewellery that the priest wouldn't have approved of."

By the early 18th century the cemetery was full and respect for the dead somewhat diminished.

Elsdon says: "One of the odd things that’s going on is by the late 17th century waste and rubbish is actually dumped in the burial ground from all the craft industries going on.

"People are presumably coming out here in the middle of the night, evading the night watchmen and dumping a barrow full of industrial waste from their small home craft industry into the burial ground."

It may have been illegal and morally dubious but this midnight practice means a wealth of material has been laying just waiting to be discovered.

Elsdon says: "We have a lot of bone work and other bits and pieces in tortoise shell and ivory and have been worked into the cemetery."

One of the skeletons found at the Farringdon site

Evidence of London life long before it was London has also been found in North Woolwich.

Fragments of stone from a “flint factory” from the Mesolithic period have given a tantalising glimpse into prehistoric life in the area.

The Crossrail project is staggeringly big. At £14.8 billion, it is the biggest construction project in Europe, building a 118 kilometre rail line and 42km of underground lines.

One of the huge tunnel boring machines (TBMs) used to create the underground Crossrail route

Five tunnel boring machines (TBMs), each one weighing 1,000 tonnes and 148m long, are currently underneath the capitals streets chewing through the earth at a snail-like 100m a week.

Progress has to be carefully planned. Not only are there other Tube lines to consider but also secret government tunnels.

Other archaeological treasures have included a black death burial pit in Farringdon, bison and mammoth bones in Canary Wharf and the UK's largest amber haul, a mind-boggling 55 million years old.