How Crossrail dug up a London treasure trove

Three weeks ago, workers tunnelling beneath London’s Soho found themselves wading through a sudden flood of water from a 300-year-old well. Unbeknown to them, the Crossrail team had breached the unmapped remains of a utility used by the capital’s 18th-century inhabitants.

The discovery of the 30m well shaft below Soho Square, which used to provide water for French aristocrats who lived in the area, was one of the more dramatic interruptions to work by long-forgotten relics of the capital’s infrastructure which have punctuated the birth of its newest and grandest one.

While the 1,000-tonne boring machines used by Crossrail to traverse London grind their way to their destination some 40m below ground, closer to the surface 100 archaeologists have been working alongside the bulldozers to sift through the capital’s soil and history.

Since work began in 2009 on the £16bn rail network – Europe’s largest single construction project – more than 10,000 artefacts have been recovered from 40 separate sites where the 73 miles of track – and 26 miles of new tunnel – that will traverse the capital are being created.

The resulting logbook of finds bears testimony to the relics of London life that lie beneath the city’s streets like an archaeological mille feuille.

While the tunnelling machines bore through bedrock dating back 50 million years – long before homo sapiens turned up in the capital – the first six metres of substrate attest to London’s two millennia of human history, with artefacts ranging from bison bones to the skulls of plague victims present in only the first few feet of soil.

Jay Carver, the lead archaeologist for Crossrail, said: “Work to relocate local utilities is providing us with a tantalising glimpse of important finds only a few metres below street level. There are locations which hold rich deposits of archaeology that provide an insight into London’s history over the last 2,000 years.”

The earliest point on Crossrail’s historical root map tells the story of some of the very first “Londoners” – returning from the Continent after the Ice Age – through the discovery of a pre-historic flint factory dating from 7,000 BC at the far eastern end of the project in Woolwich.

The discovery of more than 150 pieces of flint, including blades and offcuts, is thought to be evidence of a staging post for stone-age Britons collecting cobbles from what was then an island on the mudflats of the River Thames. After testing their worthiness as tools, it is thought the riverine collectors then took their plunder to a finishing “workshop” elsewhere.

Mr Carver said: “It is one of a handful of archaeology sites uncovered that confirms humans lived in the Thames Valley at this time. It is exciting to find evidence of humans returning to England and in particular the Thames Valley after a long hiatus during the Ice Age.”

The discoveries – ranging geographically from bronze-age flint in Plumstead and the slipways of one of the world’s most prolific shipyards in Canning Town, to Roman horseshoes found in Liverpool Street – are suitably eclectic for a city of London’s diversity.

While workers were excavating a new station in Tottenham Court Road, a cache of 8,000 Victorian ceramic and stoneware jars associated with the condiment company Crosse & Blackwell was found in a cistern close to a network of subterranean kilns and an innovative cooling system.

In the remains of Worcester House, a large manor on Stepney Green used as a centre for 17th-century non-conformists, a Tudor bowling ball was found along with shards of a chamber pot with the suitably scatological inscription: “What I see, I will not tell.”

Among the most recent finds, the first gold unearthed by Crossrail has been found in the form of a Venetian coin used as a sequin to decorate the gown or jacket of a wealthy merchant or aristocrat.

The discovery has created a puzzle for archaeologists as to how it ended up in the poverty-stricken area now occupied by Liverpool Street.

A Crossrail spokesman said: “How it found its way to what was poor east London in the 1500s is somewhat of a mystery. Archaeologists have theorised that it was perhaps accidentally thrown out in rubbish or fell off as a high-society Londoner passed in a horse and carriage.”

The cornucopia of finds is the latest example of the archaeological windfall provoked by a change to planning laws in the 1990s which put the onus on developers to fund surveys and digs whenever a building project was planned on a site of potential interest.

More than 90 per cent of all archaeological investigations in Britain are now instigated through the planning process, fuelling a rise in the number of professional archaeologists from 2,200 in 1991 to nearly 7,000 by 2007. Some 60 per cent of archaeologist jobs are now with private companies carrying out work for developers.

The result can be an excess of archaeology.

Professor Martin Biddle, chairman of the London and Middlesex Archaeological Society, who acted as consultant to the Eurotunnel project in Kent in the late 1980s, said: “There can be no doubt that a huge amount of quite fundamental material that would have been destroyed previously has been recovered and saved.

“I’m not sure all developers are enthusiastic but they now grin and bear it.

“The issue is that the economic crisis has brought a diminution in the number of local authority archaeologists who oversee this process to ensure the right balance is struck.

“If we have a site with lots of 19th century material and Roman material underneath, we shouldn’t necessarily be dedicating the same amount of attention to the later stuff as the Roman.”

It is a charge that is unlikely to be levelled at Crossrail’s archaeologists as they contemplate a veritable banquet of important excavation in the coming months, including the removal of 4,000 skeletons from a burial ground, including patients of the infamous “Bedlam” hospital, and the uncovering of a medieval tannery in Farringdon.

A Crossrail spokesman said: “It would be fair to say that we still have plenty of work to get on with.”