“The big ones smell like blanched spinach”, says Helder Esteves, who looks like he should be cleaning carpets with the large, square-sided wand he’s waving over the gravel. He’s right about the smell. In fact the flat leafed specimens he’s just boiled to death have turned an intense, vibrant green and almost look delicious. But their rude health is just an illusion: by tomorrow, they will be full deceased, and a far less appetising shade of brown.

Using steam to kill unwanted moss and weeds is a relatively new practice for the SLM horticulture team, and the initial investment was significant compared to the low cost of the more commonly used glyphosate (often branded here as Round Up). The most obvious and immediate benefit of this new steam technology is that the substance being used in this age old battle with weeds is literally safe enough to drink. But look beneath the surface, and there’s a lot more going on.