Strange unmarked activity on A4/M3 wednesday 13/11

[TRfan]

Driving central london to southampton at about 1430 on 13/11... just come off the Hammersmith flyover heading west when 2 silver unmarked skodas with sirens and blue lights passed as fast as traffic would allow.

Sometime later, around M3 J 3, same two cars passed, now at very fast speed.

Sometime later, just after M3 j7, same two cars passed yet again, possibly even faster.

Anyone seen them anywhere else that would give a clue as to what they were doing ?
.

[TRfan]

The wsapping drivers would seem to be answer as to why they kept on leaving the motorway and then zipping past again some time later. Nothing particularly exciting then. Thanks