Can you save the planet by packaging up tiny parcels of it? Idealism may have withered over a plot to stop the third runway at Heathrow but it lives on in mid-Wales, thanks to prog-rock legends Manfred Mann’s Earth Band. Some of the 100,000 people, including Emma Thompson and Alistair McGowan, who signed up to become beneficial co-owners of an orchard in the middle of Heathrow’s proposed third runway have been left fuming by the revelation that Greenpeace quietly sold the lease back to the original landowner for £1 in 2012. The charity wrongly believed it had won the battle against the third runway.

More happily, however, one of the pioneering examples of celebrities trying to save the planet by handing out little plots of land is in rather better shape than the derelict orchard outside Heathrow. Forty years ago, Manfred Mann’s The Earth Band gave away a 1 sq ft plot on a Welsh hillside to everyone who bought their album The Good Earth.

The purveyors of Blinded By the Light and other 70s classics are today as vague as any rock stars over the precise location of the 10-acre hillside near the head of the Irfon valley but they and fans who have made the pilgrimage to this elusive nirvana say it remains as unspoilt as ever.

“The first time I went, I was quite cynical about the whole thing,” says Andy Taylor, founder of the Manfred Mann fan club and one of thousands of plot owners. “I thought: ‘What can you do in the Welsh hills? No-one’s going to spoil them,’ but when I got there it was amazing.

“All these other hills have been planted with regimental lines of conifers by the Forestry Commission and it’s the one natural piece of land in the middle of it.”

Taylor has since got to know Mann, who is still touring with his band, and says the musician would “bite your ear off” if his Welsh hillside was regarded as a publicity stunt.

“He believed he was making a statement for the environment,” says Taylor. “It’s a great album, a great idea and it was meant very genuinely by Manfred at the time. I’m frequently asked which is my square foot but I haven’t got a clue – we share this piece of countryside which has been preserved.”