I used to know what it is called but I've forgotten. It's not uncommon.
It's perennial, with habit and leaves like a species geranium. The leaves
have one dark spot in the middle of them. The flower is burgundy/purple,
reflexed like a potato flower with a pointy bit sticking out the front. It
is extremely attractive to bees.
The moment someone is able to suggest what it is, I'll recognise the name
immediately, it's on the tip of my tongue and it's driving me mad!
TIA

Tina