I posted it on BirdForum for identification. It was impossible to definitively identify the bird which was juvenile though the balance of opinion was in favour of oriental honey buzzard.
Oriental honey buzzard, Najran
My friend and birding colleague, Lou Regensmorter was in Najran 10 days ago and saw another honey buzzard in almost the same place as I had seen one 10 months before.
second view of oriental honey buzzard
Once again I asked birders on BirdForum for their views. There was no mistaking this time. Lou's bird is an oriental honey buzzard. In particular you can see the all dark eyes found on an adult male bird.
Looking again at the map in the Helms guide to birds of the Middle East and you see it isn't supposed to winter within 1200 kilometres (in UAE and northern Oman). This is another incidence of under-reporting from KSA. There is a lot more here than the maps say.