What does this button do?

[Porschester]

Hi,
My 2002 2.0 tintop Friendee has one of these little round black switches with a little red light on it, the upper one in this picture. Its just to the right of the ignition switch. But it does nothing when I switch it. Ive had 'Bullseye' for 4 years now and have no idea what this does.
Can someone tell me what it does and how it works please?
Thanks, P

[g8dhe]

Its normally your rear fog lamp, a requirement in the UK, but not in Japan hence no light or switch, so there added when imported, you will need sidelights on as well for the rear fog lamp to operate