early 1950s, and consequently the site was gradually invaded by scrub, mostly hawthorn, dogwood, and wild privet. An intensive restoration programme funded by the Countryside Commission and Portsmouth City Council was initiated in 1995; large areas of scrub have now been cleared by machine, and flowers and grasses allowed to regenerate naturally. Scrub re-encroachment is controlled by cattle and horses which graze overwinter. Several species of butterfly became extinct owing to the loss of habitat to scrub, notably the Adonis blue, silver-studded blue, dingy skipper, and dark green fritillary. Others such as the chalkhill blue and small blue were at the brink of extinction, but are now flourishing again. Indeed, the hill has now probably the largest metapopulation of the small blue in the UK. References External links Palmerston Forts Society Victorian Forts data sheet on Fort Purbrook Victorian Forts data sheet on Fort Widley Victorian Forts data sheet on Fort Southwick Victorian Forts data sheet on Fort Wallington Victorian Forts data sheet on Crookhorn Redoubt Portsdown Tunnels Christ Church Portsdown Fort Southwick Fort Widley The Royal Armouries at Fort Nelson - Official Site. The Royal Armouries at Fort Nelson - Guide Conservation Management and Volunteering on Portsdown Hill - the SSSI bit History of Hampshire Hills of Hampshire Palmerston Forts Napoleonic beacons in England