Treaders - you must be used to the P180 that flits between Gloucester and Biggin regularly - such a distinctive noise.
An 12's seem to be getting more regular or are my ears more sensitive? One yesterday Keflavik to Liege. Looking at the FR24 records it'd gone across the pond via the Azores to the Caribbean then up the eastern seaboard and back via Iceland.
Woken from my slumbers this morning at 0730Z by another droning its way from Birmingham to Burgas; which I see on FR24 is due to depart for Doha shortly.