What is this Green warning light?

[Welton]

I've always wondered what this green light is? embarrassing to ask after 6 years and I could probably dig the manual out but anyone know what it means?

It's the green arrows pointing in opposite directions at the top:
http://i81.photobucket.com/albums/j218/Welton_2006/Green%20Light_zpsorcyd8j2.jpg

[marccowley]

It'll flash along with indicators IF you have a trailer connected

[Welton]

Oh I see, bit weird, thank you for the explanation.

[Snoodini]

It'll flash along with indicators IF you have a trailer connected

AND the trailer light is actually functioning, I think?

[Tony500]

For a trailer or caravan. I have two trailers and one has led lights on it and that green icon flashes with the tell tail lights for indicators but my other trailer is just normal bulbs and it dosnt flash to that.