People can be idiots behind the wheel, in or out of uniform. Police officers do a great job In general, but there are still a very few who think the shield allows them to do what they like, because they're only human. So don't take the following as a general rant against the police...
I was driving on the M40 South at 7 in the morning. The lone car ahead on me was (of course) in Lane 2 doing 60mph, forcing me to overtake at 70 using Lane 3.
A dark green Volvo S40 then approaches from behind at about 90 mph and plants himself on my boot lid, so much so that I couldn't see anything in my mirror but his windscreen, so less than a car length. I wasn't about to be bullied, so I kept my speed and safely completed the overtake, moving into Lane 1. The Volvo then pulled alongside me and the driver shook his fist at me, to which I replied with the universal hand signal to indicate he was an onanistic person.
Next thing I know, the Volvo speeds up and cuts my across nose into Lane 1, again less than car length in front of me, forcing me to brake, which he did as well, down to 60. At the same time, a board in his rear window popped up and lit up, saying "POLICE". I did nothing, just held position. About ten seconds later, the board dropped back down and he sped off, again doing 90. Bear in mind that at no point were there blues and twos, and the car was completely unmarked.
Less than a minute later, I saw the car pull into the services, so highly annoyed, I followed him in to see what was so important that he felt it a appropriate to bully me and put other motorists at risk. The answer was Costa Coffee - he needed a large latte. So I confronted him in the queue about his behaviour. After the surprise of being caught, he was unrepentant, so I demanded his name and number, got the registration number of the car, and reported him.
Despite placing the report, and following it up with three phone calls in two months, I received no confirmations, no replies, and no apologies.
Lets just say it has made my opinion of the police service somewhat less than entirely positive.