Years ago (1991) when I was working in Stanmore this plant was growing in a border outside my window. I pinched a bit and potted it up. It grew beautifully and thrived in London. Many of my friends ended up having some. It does not like growing in Scotland - too cold me thinks, and has become a bit straggly. It has peculiar looking corms, when I first saw them, I thought they were very stunted fat bumpy pink worms. So it have clover like leave which are deep purple with paler marking centres. These leaves shut at night or if put away from light. Basically they need sunshine to open up fully, and they are beautiful. The flower head is on a long stem which rises above the leaves.
I had difficulty getting photo as the leaves were closed, so had to take flower head and leaves separately. Does anyone out there know what plant it is? I am in the embarrassing position of have two people now ask me for corms and what is it called. I always just called it clover - re shape of leaves, albeit three times bigger.
Ah! I recognise that- I used to have one! The leaves fold up in the evening, and are often a nearly dark purple if they get enough light. I'll do some digging and see if I can find it... I think it's related to a shamrock, but I'm not 100% sure.
Oh Thank you rowanberry - so grateful. Gardener very happy as he has taken a couple of the corms(with leaves and flower on) to pot up and grow at home. I can tell others who have acquired bits of my plant what it is.