Bright metallic Spherical object chased by military aircraft.Bright metallic Spherical object flying at low altitude over playing fields near Lancaster University Campus. With movement and speed against the laws of physics, darted into different areas of the sky. After approx 2 minutes of this un-natural behaviour, stopped dead. All of a sudden darted off in a Northly Direction, not to be seen again.Maybe unrelated, 5 minutes later, military aircraft were seen flying low over the campus roughly in the direction of the UFO.