Chaps,
Not wishing to teach people to suck eggs but it is perfectly legal to fly lights out at night - and as a singleton - as long as you NOTAM the route. Then every other low level air user should know you are about and avoid you. This applies to dedicated user areas as well just in case someone mentions that next.
Of course he might just have not put them on by accident! It does happen!
Dooh, mmmnice got that bit out before me