This striking moth has a wide range outside Britain, but historically it was rare here and only found in the Channel Isles (thus the name) and one location in Devon.
However like many species it has been expanding its territory and has now spread north as far as Cambridgeshire, where it popped up in my garden.
This picture of the resting insect doesn't begin to show how spectacular it is in flight; sadly it didn't stay around long enough for us to video it.