A hot evening finding it difficult to sleep, In my bed I can see clearly out of my window at a large portion of the sky. Then, a light darted across the night sky at an amazing speed.I have been to many airshows and the like and am aware of the kind of speeds at which aircraft can travel, this was in a totally different league. It arched over the night sky at terrific speed emitting bright pea green light. What struck me also was the proportion of light it cast over the ground and in my room was far greater than the light source. The word 'glow' does not do it justice, it was far brighter. Comparable to modern LED police car lights flashing through a window into ones house, but perhaps still brighter, and of course in this encounter a constant light, and one must say while incredibly bright all round, as it passed me and began to go into the distance the craft seemed to emit more light from its stern side.As it passed at a fairly low altitude it most certainly hummed, and I witnessed the Doppler Effect so I am certain it came from the craft. A fairly high pitched hum, very abnormal, as I say I am familiar with aircraft the world over and this was most certainly no conventional noise such as a jet or turboprop.I lost sight of it as the width of my window naturally did not give me scope enough to see it continue its flight. I rushed outside onto my garden to see it but it had disappeared, I expected as much because at the speed it was going it was probably about another 5 or more miles away in the approximately 15 seconds it took me to get outside.5 minutes later, what was definitely a human craft flew by, I know the flight paths in my county off the back of my hand including military flight paths and over my house they travel dead West, or dead East. This aircraft was not, it was flying in the same direction as the UFO. It was far to dark to see it clearly among the clouds, it was travelling at the bottom of the cloud layer, occasionally revealing itself. Possibly an RAF Hercules, but due to their tactical role as a transporter I doubt one of those would have been deployed in pursuit of a UFO. I just can't say what aircraft it was but it was definitely a four engined propeller aircraft.I say 7 minutes in my report because that was the time with this suspicious identifiable aircraft included, but my time seeing the actual green orb blast through the sky was about 8 seconds.