Work began on Monday to repair an unstable cliff face on the south coast, which contains fossils of mammoths, woolly rhinos and primitive horses.
Teams of contractors are abseiling down the cliff face
Soil nails between eight and 15m in length were drilled into sandy chalk areas at Black Rock in Brighton.
About 1,500 tons of chalk collapsed from the cliff face in April 2001 and it has needed stabilising ever since.
Engineers abseiled down the cliffs to carry out the work, observed by conservationists from English Nature.
The agency has played a prominent role in how the stabilisation would be carried out because of the geological situation at Black Rock.
Civil engineering firm C.J. Thorne & Co was appointed by Brighton council.
Contractor Sean Taylor said: "We are at the moment putting five test anchors in which are being tested to 27 tons."
The work should eventually see 500 of the soil nails being inserted along the cliff face.
"It will protect the seafront road and help to preserve the cliffs themselves for as long as possible," said councillor Gill Mitchell at the beginning of July.