I have the M4 motorway in my Port Talbot back garden

Narelle Cowan and Aimee Lipley’s gardens have a few things in common.

Both have beautiful plants, chairs for al fresco dining and one of the UK’s busiest motorways.

Every day, around 75,000 vehicles on the main road between London and South Wales pass over the elevated concrete monolith suspended some 14 meters above their plots.

“I call it my free gazebo,” Aimee said. “I love it here, when it rains you can walk to the shops without getting your hair wet.”

The two-lane carriageway in the sky was one of the first sections of the M4, a remnant of the boom in motorway construction in the 1960s that followed the post-war boom in car ownership.