By any measure, the Roundhouse is one of north London's most famous buildings, yet it has endured a chequered history. Built as an engine turntable shed in 1847 under the auspices of Robert Stephenson and R B Dockray, the building became a warehouse for Gilbey's Gin.
In the 1960s, it became a well-known rock venue and theatre before closing in 1983.
The Roundhouse was beset by a number of abortive schemes and temporary uses for more than 20 years before rising from the ashes as a performing arts centre in 2006.
Over in Woolwich, the Grand Store depot at the Royal Arsenal is among Georgian England's finest warehouses. Following decades of neglect, it has been converted into much-coveted private apartments.
The roll call of iconic properties saved across the capital in the past two decades is an impressive one. Among them are Wellington Arch, the Albert Memorial, Danson House and Isokon Flats.
It seems staggering that such landmarks could ever have been under threat in the first place. But their revival is all thanks to what amounts to a 20-year campaign to rescue buildings at risk.
It started in London but its ripples have been be felt across the country and are now being copied across the world. First, the public was panicked by its findings, and then quickly vented its outrage.
This proved a catalyst for action that has led to the rescue and restoration of some of the capital's gems. Two decades on, it is an essential part of the heritage and conservation fabric.
In 1991, English Heritage took what it readily admits was "a bold step into the unknown". The historic environment watchdog attempted to record all grade I, II* and II listed buildings in the capital that were neglected, decaying and facing an uncertain future.
English Heritage's London and South East planning and development director Philip Davies says that while the buildings at risk register is well understood today, it was considered radical and daring in the 1990s.
"It was very clear that there were all these problems around but no-one could quantify their scale, take an overview, monitor progress, provide and direct resources or encourage local authorities. At the time there was some criticism that a central body was bashing local authorities, but this was all about highlighting priorities for them.
"We were trying to get a clear picture of the condition of the capital's historic buildings for the first time and simply didn't know what the exercise would reveal."
The first survey sparked widespread public concern. Almost 1,000 listed buildings were identified as being at risk. In 1998, the London initiative led to English Heritage starting a national buildings at risk register.
This expanded into the Heritage at Risk Register in 2008 and now covers listed buildings, scheduled monuments and archaeology, parks, gardens, battlefields, conservation areas and protected coastal wrecks. Next year will see listed places of worship join the register.
So what has been achieved in the past 20 years? English Heritage reports that 94 per cent of the buildings on the first register have been repaired, restored and brought back into use. More than 2,000 listed buildings have been replaced, restored or given a new lease of life. The proportion of buildings in the "very bad" category has fallen from 17.8 per cent to 15 per cent.
At the same time, the proportion categorised as in "poor" condition has risen from 38.3 per cent to 52.5 per cent, suggesting that while the worst cases have been tackled there remains a stubborn hard core. One of the register's biggest successes has been the reduction in the number of terraced houses at risk - down a massive 75 per cent since 1991.
The proportion of grade I and II* buildings at risk in London consistently exceeds the national average. For top-grade properties the current figure is 3.9 per cent against a national rate of 2.7 per cent. For grade II* assets it is 4.8 per cent against 3.3 per cent nationally.
The picture for other grade II buildings at risk is slightly better, with a fall from three per cent to 2.4 per cent in the past decade. The percentage of publicly owned buildings at risk has fallen from 27.2 per cent to 24.4 per cent, a figure English Heritage describes as still "unacceptably high".
The driving forces behind the decline of some listed buildings are many and varied. Almost a quarter of the buildings on the register are in public ownership. The public sector is under huge pressure to dispose of civic buildings such as libraries, swimming baths, fire, police and ambulance stations and town halls.
Falling congregations have meant that many traditional places of worship are now redundant. The capital's decline as a manufacturing centre and world port has left many industrial buildings on the register. Older schools are another source.
Much of the responsibility for stopping the rot lies in the hands of local authorities (see panel). In the first survey, English Heritage found that London boroughs were reluctant to use the statutory powers available to secure repairs in the mistaken belief that procedures would be too costly or that they would be strangled by red tape.
Today they have a wide range of such powers at their disposal. The report urges councils to deploy these to tackle repairs and blight from private buildings. Urgent works notices allow them to carry out emergency works on neglected listed buildings, while repairs notices can force owners to preserve a listed building. Amenity notices under the Town and Country Planning Act 1990, which apply to any land, can tackle neglect, disrepair or dereliction.
Other lessons learned in the past two decades include the importance of planning ahead. The report recommends that where disposal of property is planned, strategies should be put in place to minimise the risk of deterioration until a new use comes along. Short-term uses can keep buildings weathertight, it notes. "Responsible stewardship" is how English Heritage describes it.
Eighty per cent of today's building stock will still be in use in 30 years' time, underlining the need to maximise resources. English Heritage points out that 24 per cent of all waste comes from the demolition and construction industry.
Replacing a building involves a huge amount of energy, including that lost in the old structure, demolition and the manufacture and transport of materials for reconstruction.
The watchdog encourages boroughs to embed the principle of retaining buildings and improving their energy performance in their sustainability strategies.
This will be all the more important in an era of financial austerity. Indeed, there are economic parallels between the 1991 survey and the 2010 register. The collapse of the property market saw buildings abandoned and placed on the register. That is still a fear today.
Davies is painfully aware that councils are under enormous pressure to slash budgets but offers a salutary warning. He urges them to look at the benefits to the community of investing in heritage and think again before cutting conservation staff and funding. He goes so far as to insist that conservation officers are crucial to helping the government meet its localism agenda.
"Without them, far less local heritage will be rescued and removed from the register," he argues. "Resources for heritage and the built environment might be identified as easy targets but short-term savings should not cause long-term damage to the historic environment. The potential damage could take years to recover."
He concludes: "It's important to have conservation expertise in local authorities for the disposal of publicly owned property as well as in dealing with private owners.
Conservation is not a marginal extra. It's a core activity in many places and is central to a wider agenda covering regeneration, place-making and the battle against climate change. Conservation and sustainability are two sides of the same coin."
Saving London: 20 Years of Heritage at Risk in the Capital is available at PlanningResource.co.uk/doc
PROTECTING KEY ASSETS
English Heritage stresses that local authorities are central to securing the future of neglected buildings and urges them to:
- Compile their own registers for heritage at risk, including buildings and sites of local significance.
- Prepare detailed and phased action plans that prioritise buildings, sites and areas.
- Employ a dedicated officer backed by a heritage champion in areas where neglected buildings are concentrated.
- Work with regeneration agencies and across council departments.
- Repair or sell properties at risk which they own, backed by planning briefs highlighting opportunities and constraints.
- Plan for redundant buildings or sites and consider their interim use before any sale.
- Use the range of statutory powers to tackle repairs and blight from private buildings.