Blethers - Cops with cameras

Travelling south on the M74 this morning, encountered a rolling road block with the fully lit and flashing Polis car just a few cars ahead. After a couple of miles at 15 mph, the lights went off and the Polis disappeared at plenty o' quick mph. Then just a couple of miles down the road, there was the same car with the Polisman leaning nonchalently cross-legged against the back door of the BMW Touring - with the gun. Then just another couple of miles further down the road, there was an unmarked black BMW on the hard shoulder talking to the driver of a people carrying M-B Vito who had earlier sped past in the outside lane, having been delayed by the rolling road block no doubt. Conspiracy theory? Or were the Polis just needing to top up the coffers?