I had just gone out to take photos for desktop wallpaper, using a fujifilm x-t1 and xf16-55mm f2.8 zoom lens. i noticed the object within 30 metres of leaving home and resorted quickly to manual focus and aperture at 55mm (longest focal length) between f5.6 and f8, trying to zone focus. the wind was about 3 kts gusting 7 kts from around 190 degrees; the object moved almost orthogonally to the wind, heading arround 300 to 330 degrees and varying in altitude. it had a very smooth motion. towards the end of this sighting the object appeared to occult, although it was quite far away and increasingly difficult to see. while i was changing lenses to a 55-200mm, it rose in the distance and disappeared. oddly, every high-altitude aircraft in that vicinity started to leave persistent contrails thereafter, as if there had been an ambient temperature change. two "best shots" are attached, both heavy crops. the a/c in photo 2 is on the "s" curve to the heathrow flightpath and at that point is at 4000 – 5000 feet up.