Thought to be Britain's rarest bloom, what type of flower is lady's slipper?

Lady's slipper orchids (also known as lady slipper orchids or slipper orchids) are orchids in the subfamily Cypripedioideae, which comprises the genera Cypripedium, Mexipedium, Paphiopedilum, Phragmipedium and Selenipedium. They are characterised by the slipper-shaped pouches (modified labellums) of the flowers – the pouch traps insects so they are forced to climb up past the staminode, behind which they collect or deposit pollinia, thus fertilizing the flower.

Unlike most other orchids, slipper orchids have two fertile anthers — they are "diandrous". For that reason, experts have debated whether this clade should be classified within the orchid family (Orchidaceae), or whether they should compose a separate family altogether called Cypripediaceae.