An army of "heritage fans" is to be recruited to help launch a huge expansion in efforts to save listed buildings at risk of neglect or decay.
English Heritage said it hoped to recruit volunteers from next year to help survey an estimated 345,000 Grade II listed buildings - covering every possible building from barns to libraries, private homes, commercial buildings and factories.
The move comes after a successful pilot scheme using 350 volunteers who surveyed around 5,000 Grade II buildings in areas including Whitehaven, South Tyneside, Hartlepool, Leeds, Worcester, Bristol and Dorset.
Simon Thurley, chief executive of English Heritage, said volunteering was a chance to help save a historic building or improve a conservation area and could also prove a "lifeline" of help and advice for owners of Grade II buildings.
" For English Heritage it means we will eventually get, for the first time, a complete picture of the condition of all England's listed heritage," he said.
"We can use this information to decide how best to deploy our national expertise to help owners and all those tackling heritage at risk on the ground."
The drive to recruit volunteers was announced as the body launched its Heritage at Risk Register 2013 in the Granary Building, a Grade II building rescued in a redevelopment area around King's Cross in central London.
The register reveals 5,700 Grade I and II* historic buildings, scheduled monuments and archaeological sites, registered parks, gardens, landscapes and battlefields, conservation areas, places of worship and protected wrecks at risk of neglect and decay.
English Heritage said the total number on the register has fallen from 5,831 last year, with the body " well on target" to meet its challenge of removing 25% of entries from the 2010 Register by 2015.
Buildings added to the register this year include Sandycombe Lodge, in Richmond, south-west London, currently undergoing restoration, which was built by the artist JMW Turner for his father in 1813 and later served as a "shadow factory" producing airmen's uniforms.
Other sites added this year to the register include Oldknow's Limekilns in Marple, Greater Manchester, dating from 1800, but now derelict, and Green Lane Works in Sheffield, empty since 2009 but now with a "promising" future as it undergoes a £13 million redevelopment.
Baker's Hole, a palaeolithic site in Dartford, Kent, home to the earliest Neanderthals in Britain and later a chalk quarry, and described as "overgrown and overrun with animals", is also added to the register.
English Heritage said a partnership between itself and Natural England had led to the rescue and removal of 97 sites from the risk register in the last year.
These include the remains of lead mines in County Durham and Cumbria, the largest and most important Roman town in northern East Anglia, a 13th century moated manor in Staffordshire and the park and gardens of a country house in Dorset.
Other sites taken off the register include St Barnabas Church in Erdington, Birmingham, ravaged by fire in 2007 but now brought back to life by a "determined" local community; Townhead Mansion in Slaidburn, Lancashire, now successfully restored after years of neglect; and Holy Well at Trellil, Helston, Cornwall, dating back to the 15th century and now restored and repaired.