Strobilanthes angustifrons (aka Pteracanthus or possibly Goldfussia)

A deciduous shrub almost unknown in cultivation it seems. The flowers are of a rich glossy purple with a pale creamy throat. Very distinct. Flowers freely at the same time as other hardy Strobilanthes, in autumn.

Largely untried but it's proved fully hardy here on the nursery and there has been a good-sized specimen in the walled garden at Wakehurst for some time now. 

Should be much better known.

£16