Question doubtless inspired by last week's events with an An24 getting escorted into Stansted, apparently having lost comms.
It does appear that they had a flight plan from provincial France to Birmingham, this routed overhead London at altitude. They are a regular on this route. They had no issue in France (given the French did not intercept them). They were following the flight plan. They were transponding correctly at assigned altitude and track; this we know because their flight track is even picked up quite OK on amateur FlightRadar 24, right through to Stansted.
And yet the first assumption is that they are a terrorist mob going to make an attack on somewhere. This on a dark evening when the cloudbase is down to a few hundred feet and London City is experiencing many go arounds due to weather. Presumably they were all (Antonov and fighters) IMC.