Purple light moving south to north at least at 1300 miles per hour

Walking along the Northsea shore facing North, I looked back in southerly direction when a purple light caught my eye. It was a clear cloudless night, my field of vision either way would have been at least 40 miles in Southern and Nothern directions. The light travelled from South to North direction and moved over land paralel to the coastline. The light did not blink and took 3 minutes from first seeing it, to disappearing in Notherly direction. Depending on the distance from me, speed could not be determined. Yet if it had been moving overhead, it's speed would have been 80/3 = 23 miles per minute At first I thought it was a plane or a helicopter, but because there were no flashing lights, it must have been something else. I phoned a friend who at the time was the night editor for a large newspaper. When I stated: I have seen something strange, his immediate reaction  was: "did you see purple lights in the sky ?" Needless to say I was astonished and asked: have you had more reports on this? He said: "dozens of reports, but you are the only one from the West side of the country, all the other reports came from the East side close to the German border. All these people had seen formations of up to 30 purple lights moving direct North. I am puzzled to this day. john bakker (now living in Australia)
Date is approximate.  PD