Orange ball just seen in London sky

Alighted from a train i was walking in the darkness and an orange light got my attention, It was not an airplane or helicopter, i'm used to that here in London, it was a strange orange round shaped. It flew on a straight line for half of the sky and than slow down until it was standing in the same position and than became smaller and smaller until i could't see it anymore. I've tried to film it but it wasn't visible on my phone camera. I'm just curious to see if anyone else seen this strange object, I'm not looking for confirm, I know what I've seen