UFO Sighting in Caerphilly, on September 24th 2015 – White dot travelling 3 x faster than jet no sound no navigation lights @ about 20000 ft

I was walking my dog in the park at about 6 am to 6:15 am. We have a major flight path over the park and you can see and hear the jets and their navigation lights even at 35000 feet.Anyway, something caught my attention to my right. At first I thought it was a jet flying low roughly 18000 feet just below the lowest cloud. There wasn't any sound and no navigation lights. It was going about 3 times the speed of a normal jet holding its trajectory not dimming and falling to the ground like a shooting star. I watched it go over the mountain continuing its path until it disappeared. The light omitted from it was very bright but definitely not an aircraft that I've seen before.