Metallic UFO spotted over Doncaster on March 2017

On March 15, 2017 at 17:49, a metallic object was observed over Doncaster, United Kingdom. What is it?

Witness report:

My son was on our local field when he observed this object in the sky he took a picture see attached . he said it was metallic with a triangle shape below. was moving steady but was ascending.

Source, 09th January 2019