On 17/04/2021 20:41, Harry Bloomfield wrote:
It must have done at my count 40 very tight circles, before I got bored
watching. It had landing lights on, around 10 miles from the airport and
had white lights flashing on wing tips. I couldn't see any navigation
lights. What might that have been doing?

Police sometimes circle while using Stingray or similar to intercept
criminal or other suspect mobile phones, but they wouldn't normally do
it very low. I suppose they might have been constrained by the proximity
of an airport. At one time you could sometimes see this activity on
FlightRadar but now I think they have the option to prevent it being
displayed.