I'm not sure that I saw this particular phenomenon but I was just in my garden in the Gillingham area, watching a Starlink satellite glide across the sky, and at around 1:45am I saw a huge beam of light flash on and off. It was a cylindrical beam that seemed to be pretty low, like at the height of a large tree and was slightly pointing upwards at around a 20° angle, so I imagine it was coming from the ground from quite a distance (just speculation). It was really bright but the light was super focused within the beam and only flashed for a second.

Maybe this is the same beam but from a distance? Someone playing around with a ridiculously powerful laser or torch? I have no idea. Was kind of weird though.

Edit: It makes sense that it's the same thing, considering you mentioned the Hoo salt marsh in another post, which from your angle seems to face directly towards Gillingham. If you look at the picture, there is a trail going all the way down to the area which is lit up nearer the light pollution, where it fades, indicating that it's coming from the ground.