There was a time when you could spot them a mile off. In fact, there was a time when you could smell them a mile off.
Environmentalists and eco-warriors attempting to block demolition or construction works used to look like escapees from the Glastonbury Festival – Unkempt, pasty and with unwashed hair clumped into a nest of dreadlocks.
They would arrive under the cover of darkness carrying placards, herbal cigarettes, and chains with which to attach themselves to site gates or construction and demolition equipment. Simpler times.
Now, however, we are seeing a new breed of eco-warriors objecting to demolition and construction. And rather than placards, they are coming armed with something far for formidable. Science.
And while the great unwashed of years gone by could be removed with nothing more substantial than a court order, the new environmental lobby might actually prevent demolition and construction from ever making it past the planning stage.
We have reported several times about concerns over the embodied carbon contained within existing buildings; carbon that would be considered wasted if that structure were demolished.
Most recently, we saw Secretary of State for Housing Michael Gove putting a permanent block on the proposed Tulip Tower project in London over embodied carbon concerns.
And now comes the news that the same argument is being used to potentially prevent the demolition of the 1960s-built John Lewis Building in Sheffield.
Sheffield City Council is scheduled to take control of the building very soon and it is thought to be drawing up redevelopment plans.
Some estimates suggest that the cost of revamping the building could be as much as £20 million, raising the possibility that demolition and reconstruction might be more cost-effective. At least financially.
But according to the boffins at the Urban Flows Observatory, more than 4,300 tonnes of carbon were released in the production of the materials used to build the five-storey building.
To further illustrate their point, the Observatory has explained that the embodied carbon that could be lost if the building is demolished is equivalent to: 4,000 flights from London to New York; 17,000 trips by car from Land’s End to John O’Groats; or running a domestic over non-stop for 800 years.
And here’s the issue. In days gone by, local councillors liked nothing more than getting behind a regeneration project during their tenure.
Some regional mayors have staked their entire reputation upon bringing to fruition some “out with the old and in with the new” project during their reign. But the times, they are a’changing.
And now, there might just be as many votes to be won in retaining an existing building and the embodied carbon trapped within it as there used to be in the ribbon-cutting on a new building.
Tree huggers and muesli botherers were relatively easy to move. Scientists and vote-hungry local officials may not be so easily budged.