Walking this evening I looked up and saw a plane which I assumed was on approach to Liverpool John Lennon. When I looked carefully I could see that as well as the anti-collision strobes it was flashing two lights in sequence. I assumed they were the landing lights as they were very bright and positioned towards the wing tips. However, they were clearly flashing one at a time, left then right.
I've never seen this before, is it normal and does it signify anything?