Gatwick at 1150Z had: Variable 5 kn, max 16 kn, whereas Heathrow
was Calm. I don't believe either of them as there is a quite steady
5-knot NNE'ly here. Maybe Gatwick has Nearby Dust Devils and the
Heathrow anemometer needs a squirt of WD40. In any case the Gatwick
"observation" is not exactly helpful to anyone. The wind is very
rarely Variable unless it's less than about 2 kn, or in some particular
lee locations under special conditions. There is almost always a
dominant direction.

Tudor Hughes, Warlingham, Surrey, 556 ft.