Low Aircraft. Explanation?

[Riation]

It was about 2030, 18th Feb and I was going down the motorway (as a passenger), when I noticed an airplane's lights in the sky in front of me, quite low. It looked unusual since, although it was night, and dark, the only lights on were the red and green wing lights. As it got nearer, I saw it was quite large; 2 engine commercial jet size. Then I noticed, flying a few wingspans ahead of it, there was another similarly sized airplane, but with all its lights off... It looked like formation flying; but with few and no lights, and so low?
We were about 51.480, -1.302 (tx Google!) and their heading was roughly 180 to 220, judging by their direction relative to ours and the road.
Perhaps it was military practice.
Any ideas?

[chiglet]

I could tell you, but it is pointless...as the large black car has just parked outside your house.......:ouch:
watp,iktch