Terry Driscoll and Stephanie Slann first found the bizarre-looking growths in their lawn in Caversham, near Reading, in mid-July.

When more of them started popping up, Terry contacted the Berks, Bucks and Oxon Wildlife Trust (BBOWT) to report the unusual finding, which has now been confirmed as a rare red cage fungus, clathrus ruber - also known as the lattice stinkhorn because of its putrid smell.

Terry, a management consultant and trustee of the wildlife charity AfriCat UK said:

"When I first saw one, I thought it was a chewed-up dog toy, but they smell like rotting meat - the flies are straight on it. The other members of my family who are into wildlife have been very impressed.”

Terry contacted his sister-in-law, who is an ecologist, and she identified it as a rare stinkhorn fungus. Common in southern Europe, the species is rare in mainland Britain, and generally thought of as an introduced species.

The National Biodiversity Network (NBN) only has five accepted sightings of the fungus in the UK on its online atlas, though there have been more unconfirmed reports.

When Terry and Stephanie's dog started sniffing the rancid-smelling fruiting body, Terry feared he might eat it and get sick, so he plucked the globe and threw it away. He also mowed the grass in that area - however, more of the orbs started sprouting up - each one starting as a small, white sphere and growing to about the size of a golf ball, then splitting open to reveal a gory-looking interior.

The couple have now counted 13 of the crimson cages sprouting up on their lawn. They have reported the outbreak to the Thames Valley Environmental Records Centre (TVERC), the British Mycological Society (BMS) and BBOWT.

Andy Coulson-Phillips, BBOWT Ecology Officer, said:

"This was a really striking find, and we are glad that Terry and Stephanie reported it. Clathrus ruber is generally considered to be a native of warmer southern Europe, so it's interesting to see it popping up in Berkshire.

“It's also important to keep a record of where uncommon species like this appear, so we can build a picture of how our natural environment changes over time. It also just goes to show that you never know where you might make an exciting wildlife discovery, so it's always worth keeping your eyes open."

Having established that the species is not considered toxic or dangerous, Terry and Stephanie have decided to let it carry on growing in their lawn - the latest outpost for the Mediterranean mushroom in the UK.

Find out more about the unusual fungi and mushrooms that grow in our area on the BBOWT fungi pages.