Click on Google images 'Voodoo lily' and see if you think that fits the bill.

It looks rather like Dracunculus vulgaris, wghich can be known as Voodoo Lily or Dragon Lily. As to how it got there, it can only have been deliberately planted, surely?

The only thing better than the wonderful appearance is the alluring fragrant smell. An ideal specimen for 'cut flowers' and bringing into the house!
(Wicked joke, as the flower is designed to attract flies with its 'distinctive' smell!)

Somebody must have planted it at some time (perhaps you are new to your garden) but I've found ours went 'dormant' for a year or two and has only come back after a better less dry spring.

it smells of rotting flesh!)(I remember a gardening friend having a clump of these voodoo lilies, she used to call them "the dead rodents flower"...) - but it does look rather spectacular, doesn't it?

Thank you dear gardeners we are most grateful to receive your answers. What an excellent "club" to belong to!!

Bulbaholic we remain amazed - this wasn't planted.
We bought this house with a derelict garden 9 years ago and within 3 years transformed it into sectionalised plot with trees, shrubs and areas of perennials. Lots of fun lots of hard work.
We had seen Gaura the bee balm in Germany and Australia and invested in one white and one red last year. The supplier in Cornwall suggested they were winter hardy.
However with temperatures down to minus 14 degrees last winter it was no surprise to lose both plants.
In July we noticed that the red variety was growing well in another concealed location some 30 metres distant.