Huge glowing UFO caught over the sea in Wales

On July 23, 2017, a witness took a photo of a huge bright UFO flying over Amlwch, situated on the north coast of the Isle of Anglesey, Wales. What is it?

Witness statement:

Only seen object on two separate pictures from myself and my partner when we were cross checking our photos
We cannot make any sense of the picture - initially thought UFO.