Ask any motorist what they think of unmarked police cars patrolling the roads and you're likely to get the same answer: They're unfair.
Camouflaged amongst the traffic, these police cars scour the roads catching law-breaking motorists completely unaware that they were ever being followed.
It's easy to see why motorists think they're a little underhand. So, in an attempt to uncover their mystery work, we've been behind the scenes with the Roads Policing Unit, based in Havant in Hampshire, to see what really goes on.
I spent the night in a BMW 330d unmarked car. It's a dark grey and totally unremarkable looking saloon – in fact it looks like any other rep-mobile pounding the UK's motorway network. It's easy to see why it's so efficient.
"These new cars are impossible to spot," explained my host for the evening, PC Chris Powling, of his 63-plate Beemer. He's been with the force for 26 years and a traffic cop since 1997.
"When I started we were using Volvo T5s – a great car – but even our last unmarked vehicles, the Skoda VRS, were easy to spot if you knew what you were looking for. They had extra aerials and the cameras and blue lights cut into the bumper gave them away.
But you'd need to be pretty sharp to spot that. Even to a motor journalist's eye there's very little to give the car away as police – even the ANPR camera is hidden behind the number plate, viewing passing traffic through one of the letters which is mirrored.
It's effective too. We head out on to the M27 and within minutes have caught our first offender. He's recorded doing 92mph over a distance of nearly a mile in a Vauxhall Vectra.
PC Powling pulls him over and issues a fixed penalty notice – that's three points and £100 fine.
"It was his birthday," he explained after he's dealt with the offender. "Now he's got a £100 gift voucher from Hampshire Constabulary."
The driver had been caught the week before doing 53mph in a 30mph and obviously hadn't learned his lesson.
"That's what the unmarked car is for," explains PC Powling. "It's to target those persistent offenders who would never be caught by a marked car because they slow down, but as soon as it's gone will go back to driving at dangerous speeds."
We head back on to the M27 at Eastleigh and within seconds we're passed by a BMW 7 Series traveling in excess of 110mph. PC Powling is quick to get the unmarked car up to speed and attempts to record the offence on the car's Vascar unit.
This box of tricks records speed over distance and needs two fixed points for the offence to be marked. It proves tricky as the BMW is travelling too quickly and is too far ahead to be accurate, but that doesn't stop PC Powling following the car home.
We pull up behind him and the driver's face when he sees a police officer step out of the dark BMW that bas been tailing him for several miles is one of shock and surprise.
PC Powling issues another fixed penalty notice using his car's calibrated speedo as evidence. "This isn't what we'd normally do, but I have clear evidence he was breaking the speed limit – and two witnesses," he explains. "On the ticket I put 90mph plus."
As we rejoin the motorway at Hedge End, Powling explains his pet hates as a traffic officer. Number one is drink drivers.
"How anyone can be so ignorant to get behind the wheel drunk is a mystery to me," he says. Number two is using a mobile phone behind the wheel and number three is speeding – and he's specifically talking about the ones that do it in three figures.
But what does Powling think of those who accuse the force of being sneaky by using the unmarked cars?
"We don't hide in these unmarked vehicles, but they blend in and help us catch those serious, persistent offenders that might not otherwise be caught," he explained. "They help make the roads safer.
"At least one officer from our base in Havant is out in the unmarked car every shift, so it's in constant use."
We head into Portsmouth on the M275 and follow a VW Polo that doesn't slow down for the 60mph limit. He's travelling at 70mph as we follow him into the 50mph zone, so PC Powling pulls him over. This time he's captured the offence on Vascar.
The young driver is a referee who's just been at a football match in Gosport. "Now we've given him a red card," jokes PC Powling. By that he means another fixed penalty notice and some "education" on the rules of the road.
I'm impressed with how fair PC Powling is with every driver he pulls over. He's polite, efficient and authoritative. I'm surprised at the reactions from the drivers too. At first it's one of surprise that the guy in the BMW is a police officer, but by the end of their chats most shake the officer by the hand.
"It's not always like this," says PC Powling. "Tonight people are being particularly polite."
I wonder if drivers give him stick for "sneaking up on them" in his unmarked car. "Not really," he explains. "People know we use these cars they're just usually ashamed they've been caught."
PC Powling dispels a few urban myths while we're driving back to base too. The first is the misconception that you can't be done for speeding if there's only one officer in the car.
"That's rubbish, we usually work alone," he says. "Another I get is you can't give me a ticket because you haven't got a hat on. That one is certainly not true either!"
Although my time with PC Powling and the unmarked BMW is short it's an interesting insight into the work he and his colleagues do.
I admit I was one of those who originally thought these cars were a little unfair, but having spent a few hours riding alongside the officers I can now see that they're a vital tool in increasing road safety. With unmarked cars like these patrolling our roads the chances of the idiots on the road being caught are far higher. That, in my book, is a very good thing.
Unmarked Bikes Too
The unmarked BMW is not the only weapon in the unmarked police arsenal – they've got a bike too.
PC Phil Robertson shows me around the unit's Kawasaki 1400 GTR. A big bike capable of 152mph, it's been on the fleet for a year. Its blue lights are very well concealed, but the officers still have to wear high visibility clothing when riding it.
"It has a camera on the front that records the speed and stores it on a USB stick," explains PC Robertson. "I then plug that into a tablet and play it back to the driver or rider we've pulled over. No one has ever contested the evidence in court."
The force uses the bike to target bikers on high-risk routes – like the A272 and A32 in Hampshire – and it's proving to be very effective.
"It helps that it goes like a spaceship," adds PC Robertson.
Having trouble spotting the latest generation of unmarked police cars? Check out this handy guide here.