Moving very fast east to west, diamond shaped with long tail, definately not natural.Whilst waiting for brother in law on the car park of the Crowne Plaza Hotel, Heathrow, London. The sun was over the horizon as dawn had broken shortly before. I then saw a white/blue diamond shaped object with a long tail moving East to West. At first I assumed that it was a meteor and would burn out, but it did'nt it kept moving very fast. I shouted to my brother in law "((name deleted)), look" and pointed, he turned to look. We then both saw the object pass through an aircraft contrail which was'nt at a great height. This meant to me that it was'nt at the great altitude that I originally thought it was! The object then disappeared over the horizon. ((name deleted))'s first words to me were "Do you think that was military" (He obviously did'nt think it was natural). I replied "Not at that speed" Background of first observer, 30 years in the British Military, second observer building project manager.((FOLLOW-UP COMMUNICATION WITH WITNESS))Dear Peter,Thank you for your prompt response. You are correct on both counts, it was also definately not a natural occurrence. The reason I took so long to report it was that I expected it to be on the national news, as I thought hundreds of people must have seen it as it virtually flew right by one of the busiest airports in the world. Regards, ((name deleted))((END))