Bears would often come across North of Scotland as a pair, one 10nm behind the leader. A Tanker, Victor or VC10, might close up on the leader, whereupon the no2 Bear would sneak up behind and try to sandwich the Tanker between them, happened to me once. Certainly the Bears large performance range could make it very difficult to stay with them if they chose to try and get away though they generally just noisily ploughed on their way. They appeared to fly to metric levels and ignored normal ATC rules.