The Greywell Tunnel is a 0.6 hectare

Hectare

The hectare is a metric unit of area defined as 10,000 square metres , and primarily used in the measurement of land. In 1795, when the metric system was introduced, the are was defined as being 100 square metres and the hectare was thus 100 ares or 1/100 km2...

 biological Site of Special Scientific Interest (SSSI) in Hampshire

Hampshire

Hampshire is a county on the southern coast of England in the United Kingdom. The county town of Hampshire is Winchester, a historic cathedral city that was once the capital of England. Hampshire is notable for housing the original birthplaces of the Royal Navy, British Army, and Royal Air Force...

, England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

, notified in 1985. When opened in 1794 it was the longest tunnel on the Basingstoke Canal

Basingstoke Canal

The Basingstoke Canal is a British Canal, completed in 1794, built to connect Basingstoke with the River Thames at Weybridge via the Wey Navigation....

. It was closed due to a roof fall in 1932.

History

The tunnel was required to avoid the land of the Rt. Hon. Earl Tylney to the north, where a contour-following route had been surveyed but could not be followed due to his objections. Construction started in October 1788 and the canal was opened on 4 September 1794. The last successful navigation was in 1912 and the tunnel was finally closed when the roof collapsed in 1932.

SSSI

The tunnel is of interest for its bat populations: it has more roosting bats than any other site in Britain. The species involved are Natterer's Bat

Natterer's bat

Natterer's bat is a European bat with pale wings. It has brown fur, also seen on the leg wing membrane, tending to white on its underside...

 (Myotis nattereri), Daubenton's Bat

Daubenton's bat

Daubenton's Bat, Myotis daubentonii, is a Eurasian bat with quite short ears. It ranges from Britain to Japan and is considered to be increasing its numbers in many areas.The name commemorates the French naturalist Louis-Jean-Marie Daubenton....

 (Myotis daubentoni), Whiskered Bat

Whiskered bat

The whiskered bats Myotis mystacinus and related species, are small European bats with long fur. Although uncommon, M. mystacinus is often found around human habitation and around water; it is similar to Brandt's bat Myotis brandtii, from which it was distinguished as a separate species only in...

 (Myotis mystacinus), Brandt's Bat

Brandt's Bat

Brandt's Bat is a species of vesper bat in the Vespertilionidae family.It is found throughout most of Europe and parts of Asia.It is named for the German zoologist Johann Friedrich von Brandt.-Echolocation:...

 (Myotis brandti) and Brown Long-eared Bat

Brown long-eared bat

The brown long-eared bat or common long-eared bat is a fairly large European bat. It has distinctive ears, long and with a distinctive fold...

 (Plecotus auritus).

Sources

• SSSI citation sheet for Greywell Tunnel, Natural England
  Natural England
  Natural England is the non-departmental public body of the UK government responsible for ensuring that England's natural environment, including its land, flora and fauna, freshwater and marine environments, geology and soils, are protected and improved...
  
  website, retrieved 18 July 2010