WORK to conserve and stabilise Silbury Hill has begun this morning.

English Heritage, working with specialist engineers, has exposed the door in the side of the landmark leading to the tunnel excavated by Professor Richard Atkinson in 1968.

Working from a specially constructed platform built on the south west side of the hill, the project team has cut away the turf surface of the hill to a depth of some three metres, revealing the doorway used by the professor and his team.

The team are planning to reuse the steel supports inserted by Atkinson and remove the 4,400-year-old hill's less stable backfill before filling in the void with chalk.

Engineers will also remove support arches to return the structure to its original Neolithic condition.

Dr Bob Bewley, English Heritage's regional director for the south west, said: "The engineering and archaeological works about to start here at Silbury Hill are the result of many years of meticulous research and planning.

"The hill has been a stunning part of the Wiltshire landscape for 4,400 years and we hope that the work we do this summer will stabilise its structure and keep it safe for many years to come.

"It is a privilege for us to be able to get so close to the people that originally built the hill, through the work we are doing over the coming months deep inside it."

The other two major components of the stabilisation work are the excavation and refilling of the crater on the top of the hill, formed when the shaft sunk by the Duke of Northumberland in 1776 collapsed in 2000, and the filling of a number of craters and depressions on the side of the hill.

In March, archaeologists found traces of a Roman settlement at the landmark.