I am the original poster. Although I called it the "parking brake light", technically it's just the "brake indicator panel light" (but not ABS light).
Reading the manual (gasp!) gave no indication (pun intended..), but I did eventual find a post on-line, as suggested in a response above, that it also indicates low brake fluid. On inspecting the resevoir, it was low, and when filled a small white plastic float could be seen rising, almost certainly the contact with the sensor embedded in the filler cap. Problem solved (although low fluid, without any leaks, may well suggest I need to have brake pads & rotors inspected for wear!).