Some heritage sites in the UK that are difficult to preserve should be left to decay, says a leading academic.
Climate change and tight budgets, among other factors, may mean that some heritage sites cannot be protected, according to Caitlin DeSilvey, of the University of Exeter.
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She suggests that if a heritage site has to be lost, rather than see it as a failure, it should be seen as a deliberate decision to let nature take its course and learn from the change.
Speaking to The Times, Professor DeSilvey said: "There is room to explore more creative approaches in how we care for heritage.
"What happens if we choose not to intervene? What possibilities emerge when change is embraced rather than resisted? What if we allow things to become ruins?
"Processes of decay and disintegration can be culturally - as well as ecologically - productive, but we also need to recognise that people have very strong feelings about these places, and those need to be considered as well."
She added: "This approach only applies in certain circumstances: when preservation or repair is not possible or realistic due to cost or other issues."
According to the Telegraph, the National Trust spent £72 million overall on property projects in 2015/2016. It gave £466,918 on works at St Michael's Mount, a Cornish island home to a medieval church and castle.
Professor DeSilvey cites the former atomic weapons testing facility at Orford Ness in Suffolk as an example of letting nature take its course at some sites.
The shingle spit was a secret military base for the MoD in the Second World War, and is now a nature reserve managed by the National Trust through a process of "continued ruination".
Prof DeSilvey said: "Orford Ness is an interesting case because it shows that we don't always have to associate ruination with failure and neglect.
"Where the process of physical decay is going on, and nature is moving in, we can try to see this in a positive light and ask ourselves what we can learn from those changes."
She suggests that this process could be followed at other sites, possibly like Mullion Harbour (pictured top) in Cornwall, where £1,500 a week is spent on protection and maintenance that is becoming increasingly difficult.
She said: "One way to think about places like Mullion is to consider how we could mark the 'afterlife' of the harbour by re-using its materials in other structures, and remembering its passing in that way.
"It's hard to let go and I am asking how we can do this gracefully and attentively."
Phil Dyke, coast and marine adviser for the National Trust, said: "We're committed to protecting historic buildings and structures when it is realistic - but at the same time making sure we understand, record and celebrate the significance of those that are most at risk of being lost."