NEXT time you travel along Hornchurch rail line you might just feel a chill of excitement – after scientists rediscovered it as one of the most important Ice Age sites in Britain.

The full significance of the railway cutting - adjacent to St Andrews Park, in Hornchurch - is being revealed in a joint project between Network Rail and Natural England.

Now the cutting, officially a Site of Special Scientific Interest (SSSI), will feature in The Birth of Britain - a new Channel 4/ National Geographic International series, presented by Tony Robinson,

Hornchurch’s importance lies in the geological deposits it reveals.

The Hornchurch Till - or glacial deposit - contains Jurassic rocks and fossils carried from the Midlands, showing the site marks the southernmost extent of the Anglian ice sheet which covered much of Britain, reaching north London around 450,000 years ago.

The cutting also reveals the Thames was diverted south from its former course through East Anglia by the ice sheet, into its present valley through London.

The discovery of the site was made during construction of the Romford to Upminster branch line in 1892 by the geologist TV Holmes, of the Essex Field Club.

Re-excavation of part of a section in the cutting in 1983 confirmed the site’s significance.

In recent years the site had become overgrown but extensive clearance has revealed the cutting face and the trench excavated in 1983.

Emily Dresner, land management and conservation lead adviser for Natural England in London said: “It’s been amazing to see the history of the site uncovered. The latest achievement is the mapping of the precise join between the till and the overlying Thames gravels along the length of the cutting.”

Natural England and Network Rail are currently ensuring the geology of the site is preserved and available for future study.

John Whitehurst, infrastructure maintenance director for Network Rail, said: “Helping protect and preserve one of the most important Ice Age sites in the country just yards from a 21st century railway has been an exciting challenge for my team.”

The show will broadcast at 8pm on Channel 4 on January 24.