Dotsie wrote:Is it the prime meridian laser?
We have a winner! Or we would have, if you hadn't changed your answer. That's OK, I'll eat your prize for you.
It's the meridian laser at Greenwich Observatory, taken from about 15-20 miles away. That's Canary Wharf centre frame. There is a footpath local to me where you can get a tiny glimpse of London.
Think I need to crop the image down vertically to make a wide panorama to make the most of it. I might also photoshop out the foreground lights so I'm just left with 4 elements: the outline of the horizon, the cityscape peeping above it, the ribbon of cloud and the laser beam.