Research soon established that this was the lousewort - Pedicularis sylvatica -
not a rarity by any means but an interesting plant all the same. A lover of acidic bogs in sunny areas, this plant is semi-parasitic, taking nutrients from the host plants around it.
The name lousewort refers to the lice and liver-flukes that often inhabit the places in which the plant grows, sometimes infesting grazing animals, and occasionally humans.
The plant is evidently a useful skeletal muscle relaxant and has been used herbally to help
overcome back and neck pain. Not too sure whether I would want to try it!