This photo shows several features well, but is misleading in one. The upperwing didn't have the "flash" that it almost appears to have here. Only the outer two primary shafts were white, although the white vanes of the next couple of feathers could sometimes be seen in flight, this is what is visible here. The rounded shape of the central tail feathers could be seen on close views, but not in any of my photos.

The bird was very crisply barred black/white on both the uppertail and undertail coverts, as well as underwing coverts, axillaries, and some on flanks. Parasitic tends to be more weakly barred. The plumage tones could change with lighting and angle, but was always a "cold" grayish tone, not the warmer rufous tone often shown by Parasitic. Note the crisp, pale edgeing on the upperparts. The underwing flash is extensive for a Long-tailed, and visible from a great distance. The uppertail barring gave the uppertail an overall pale appearance which also could be seen from a long way off.

This bird soared much more than I was expecting, and at times this allowed good views of the wing base to tail extension profile. It was a real treat being able to spend good quality time with this bird, and even see it put on a sudden burst of speed to harass both a Caspian Tern and an Osprey at different times!