Bright rectangular UFO over Cardiff, Wales

On November 5, 2017, a rectangular-shaped UFO was photographed over Cardiff, Wales, by an automobilist. What is it?

Witness report:

I was travelling east on the M4 motorway between Cardiff and Newport in South Wales on Sunday 5 November 2017 at approximately 4.05 pm. In the sky to my left was a white object which did not appear to be moving. I took 2 photos on my iPhone 7 but they are not very clear. Once home, I enlarged the images and saw that the object was definitely nothing I recognised, appearing as 4 vertical rectangles side by side. Had I been alone I would have pulled off the motorway to view the object further, but unfortunately this wasn’t the case.