A rare plant has allegedly been stolen from the Royal Botanic Gardens at Kew in west London.
The Metropolitan Police said a Nymphaea Thermarum, the smallest water lily in the world, was taken from the Princess of Wales Conservatory last Thursday.
It is believed to have gone missing at some time between 08:30 and 14:55 GMT.
The plant, which is now extinct in the wild, would have had to have been dug or pulled up from a shallow water lily pond, the Met said.
Discovered in 1987 by German botanist Prof Eberhard Fischer in one location in Mashyuza, south west Rwanda, it grew around freshwater hot springs and needs warm, damp mud.
But the thermal water lily disappeared from the site in Africa about two years ago "due to over-exploitation of the hot spring that fed this fragile habitat", the gardens' website said.
Kew is one of the places where the water lilies are cultivated.
The rosettes are about 10-20cm wide, bearing white flowers with the leaves can be as little as 1cm in diameter.
Richard Barley, director of horticulture at Kew, said: "Our staff are dedicated to the conservation of plants and when incidents of this nature occur it is a blow to morale.
"We take theft of our invaluable scientific collection of plants very seriously."
Anyone with information is asked to contact Richmond upon Thames Borough police.