The various pieces of legislation used for legally protecting heritage assets from damage and destruction are grouped under the term ‘designation’. The protection provided to scheduled monuments is given under the Ancient Monuments and Archaeological Areas Act 1979, which is a different law from that used for listed buildings (which fall within the town and country planning system). A heritage asset is a part of the historic environment that is valued because of its historic, archaeological, architectural or artistic interest. Only some of these are judged to be important enough to have extra legal protection through designation.
There are about 20,000 scheduled monuments in England representing about 37,000 heritage assets. Of the tens of thousands of scheduled monuments in the UK, most are inconspicuous archaeological sites, but some are large ruins. According to the 1979 Act, a monument cannot be a structure which is occupied as a dwelling, used as a place of worship or protected under the Protection of Wrecks Act 1973. As a rule of thumb, a protected historic asset that is occupied would be designated as a listed building.
Scheduled Monuments are defined in the Ancient Monuments and Archaeological Areas Act 1979. In England, Wales and Scotland they are often referred to as a scheduled ancient monument, although the Act defines only ancient monument and scheduled monument. A monument can be:
In Northern Ireland they are designated under separate legislation and are referred to as a scheduled historic monument (for those in private ownership) or a monument in state care (for those in public ownership).
The first Act to enshrine legal protection for ancient monuments was the Ancient Monuments Protection Act 1882. This identified an initial list of 68 prehistoric sites that were given a degree of legal protection (25 sites in England, three in Wales, 22 in Scotland and 18 in Ireland). This was the result of strenuous representation by William Morris and the Society for the Protection of Ancient Buildings, which had been founded in 1877. Following various previous attempts, the 1882 legislation was guided through parliament by John Lubbock, who in 1871 had bought Avebury, Wiltshire, to ensure the survival of the stone circle.