A retired couple may have accidentally found the ultimate example of green energy - by covering their house in a climbing plant.
Michael and Teresa Lye did try to tame the Virginia creeper when they first moved into the home in Bromley, south east London, nearly four decades ago.
But over the years they have simply stopped trying and are now content to let it grow, asking a relative over infrequently to prune the leaves covering the windows.
The plant, also known as five-leaved ivy, is somewhat of a local attraction - with people regularly stopping to take photos.
But the pair say it has a practical purpose too - keeping the house warm in the winter.
Michael, 75, said: "We think it acts as natural insulation.
"But I'm still dreading my gas and electricity bill coming."
Teresa, 72, added: "This room is nice and warm. Go in any of the rooms - it's warm. That's why we've got a fan in here. In the winter we are toasty.
"My daughter comes up and says, 'You got the heating on?'. I say, 'No, of course we haven't got the heating on'."
The parents-of-five and grandparents-of-25 bought the semi-detached property for £24,000 in 1984.
It is located on an estate in the Downham area, which they say dates back to 1928 and was opened by royalty - who suggested the Virginia creeper.
But when the couple viewed the house decades later the plant was running amok - and had even made its way inside.
Michael, who worked in social housing, said: "A monarch opened the estate. I can't remember which one.
"And they said, 'These houses would look lovely with Virginia creeper on them'.
"So the council started to plant it on all the houses. Most people moved in and got rid of it.
"[When we viewed the house] there were some windows that were broken, and [the plant] had grown up the top passageway along the wall.
"It had actually come in the house."
Teresa said: "It had grown in one bedroom, where they [vandals] had broken the windows.
"When we viewed it, I said, 'Oh'. You walked in the room and it was right across the ceiling and down the walls.
"And they said, 'No, we're going to clear all that. We're going to paint the window, we're going to decorate'."
Pictures of the house often make their way on to community Facebook groups, where people speak fondly of the local landmark.
Michael added: "Every week, somebody will stop.
"If you watch the cars pulling up because of the lights, you can see them doing [makes photo gesture].
"As early as last week a van with two people in it - a low, flat truck - was going past slowly and the guy took a picture as he drove past.
"Then there was a lady out there the other day. I said, 'It's a pound a picture'. She said, 'What?!'. I said, 'I'm only joking, don't worry'.
"And she asked, 'Don't you get all the creepy crawlies coming in the windows?'. And I said, 'No, the wife sleeps with her mouth open so we're fine'."