Somewhere in almost every British lawn there is a plant that most people mow without noticing.

It is small and creeping and does not present itself dramatically. Its leaves are oval, slightly wrinkled, dark green, easy to read as ground cover rather than anything in particular. In late spring it sends up a short flowering spike from which tiny purple blossoms open in whorled rings around a tight oblong head. Each flower is hooded, two-lipped, with white markings on the lower petal that make it recognisable once you have learned to look for it.

But most people never do learn to look for it.

They mow it every fortnight throughout the summer, year after year, for the whole length of a gardening life, without knowing its name.

Its name is Self-Heal.