IMAGINE eating a 7oz steak, stopping off to fill up your car on your way home and then later winding down with a Smirnoff and coke in the pub.

It sounds alright, as long as you’re not vegetarian, no? Except, your steak arrived on the plate looking meagre, your petrol receipt seemed higher than usual and you suspected you were sipping a watered down drink.

Who you gonna call? Step forward Trading Standards: men and women who make it their work to fight against rogue traders and dodgy deals.

I spent the day with Matthew Bartlett, 43, a senior trading standards officer with Torfaen Council, who specialises in weights and measures.

Our first assignment was in Pontypool Market, where we stopped off with Wayne Randell the butcher to check his scales were in working order.

First, I had to put on a fetching hairnet, hat and white coat before I could go behind the counter with a heavy black box that looked as if it could contain money or a weapon.

In fact it had a set of calibrated weights inside.

The standards for industrial scales are more rigorous than, for example, a bathroom scale or one you might use to measure out flour in your kitchen.

To check accuracy, we built up the silver weights on the scale then took each away one by one to check if there were any discrepancies.

Then we tried the eccentricity test. It’s not about how many odd socks you wear or whether you can solve mathematical equations only if standing on your head, but about whether the scale is accurate in each place.

First the display showed exactly 200g. This was good news. It went up to 700g as we added on the 500g weight: again, a good result. As the numbers crept up I thought we were going to present Wayne with a perfect bill of health for his scales, but error crept in on one corner when it was measuring 5g less than what was there at 5kg. There was no need to suspect any foul play as this meant customers would be getting a very small amount for free if the food was weighed out in the bottom right corner.

This is within a permissible margin of error, however, so Mr Bartlett tells me Mr Randell gets a “big tick with that one - we’re happy with that. If the machine wasn’t accurate we would put a sticker over the verification code and it would become a criminal offence to use it.”

Not everyone welcomes the unannounced visits from the council, but Mr Randell said he doesn’t mind although says they can be a bit nerve-wracking, adding: “Where the health and safety side is concerned, the rules are changing all the time. It’s a job to keep up to be honest. I left school to get out of bookwork”

We headed next door to Phil’s Pantry, a delicatessen. Phil bought brand new scales after the last inspection showed there was a problem. One of the scales was perfect but the other had a slight issue, although only at weights of above 6kg. As Phil pointed out, no customer would ever come in to buy 6kg of pork pies or similar, or at least he hadn’t experienced it in his career so far.

Mr Bartlett noticed a slight problem, as Phil labels his food £1.60 per gm.

“That’s not a valid measurement,” Matthew said. “It should be by the g or gram.

I wondered if maybe I was about to witness some action, perhaps some signs being seized or stickered over, but Mr Bartlett said: “No council would ever take anyone to task for writing ‘gms’ instead of ‘grams’.

"It’s only when people are out to defraud the public, that’s when we would consider prosecution.

“All we want businesses to do is comply. You can treat this job the way you want. You could be quite ruthless, go in and say “This is wrong.” But you want to work with businesses. It’s a win-win situation; they have confidence in their equipment and as a customer you rely on the fact someone is checking them.”

Scale inspections usually take place one a year, although they will be more frequent if the council receives a complaint.

After checking out the post office, which was all ok, we drove down to the Ashbridge Inn between Pontypool and Cwmbran to check they were pouring the right drinks in the right quantities.

When Mr Bartlett told me we would be testing Smirnoff I thought my day might be wilder than usual but he scotched the idea there would be any taste test when he got out tubes of litmus-type paper. Brands like Smirnoff, Gordons and Bombay Sapphire include certain chemicals in their products so you can test if it is genuine rather than watered down, or a cheaper house version poured into a more expensive bottle.

We inserted the paper into samples from each bottle for 10 seconds, left it to dry and checked which colour it turned.

All the spirits we tested were the real deal, although one of the tests turned a murky greenish yellow rather than the hoped-for green, which I wasn’t sure about.

Matthew put the pressure on, telling me it’s my call: “Do we want to seize the bottle in front of the public?

I decide on balance it is green.

We then checked the glasses for verification signs to show they’re the correct measurement and tested the spirit measures on each bottle, known as ‘optics’. Luckily the punters at the Ashbridge are getting the correct amount.

At the pub we found the store cupboard full of bottles ready for use. Each bottle of spirits has a patch which will glow fluorescent if it is a genuine bottle on which UK duty has been paid. Mr Bartlett took out a light which we shone on the bottles. All of them glowed eerily in the dark cupboard and so we took our leave of the pub.

Apparently the amount of people cheating by switching cheaper spirits has fallen in Torfaen.

“When I first started it was quite a usual fiddle,” Mr Bartlett said. “But over time people see us doing the tests. At the moment we’re on zero per cent fails.”

We picked up a van to head to the David Taylor Garage on Albion Road to test out the petrol pumps.

“This is one of the most dangerous jobs”, Mr Bartlett warned. “The biggest risks are fire or explosion, or being struck by a moving vehicle.”

After we both put on a protective boiler suit, safety shoes and fluorescent jacket and cordoned off part of the forecourt, we started testing whether the petrol pumps were giving the right amount.

The containers we used were precisely measured to hold exactly five, 10 and 20 litres, with an overflow lip to see if the pump was over or under.

This was the most physical part of the day, as I felt like I was hauling vats of petrol across the garage before tipping them back into an underground storage container so it wasn’t wasted.

Most of the pumps were fine, but Mr Bartlett had concerns about one of them, selling Super Unleaded.

We stopped when the dial reached 10 litres, but the vessel was still short of 50 ml. Then the dial jumped a little so it looked as if we had paid for more than 10 litres but in fact hadn’t got enough.

Mr Bartlett said he was a little surprised he hadn’t received any complaints, but said as it was the most expensive petrol it wasn’t likely to be very popular.

He checked nobody has tampered with the scale by opening up the pump. A lead seal he himself installed in 2008 is still in place, so says he is satisfied this is not an attempt to diddle the customer but due to wear and tear.

It was possible the numbers flicking up was caused by hose dilation, Mr Bartlett said, so he recommended the pump be looked at even though it was still legal.

Before we left, the manager put an ‘out of use’ sign on the pump and said he would check it out.

We headed off. It was an interesting day; I will never take a set of scales for granted again. Mr Bartlett joked that at the end of the working week he wouldn’t go to the pub for a drink, he would have “an intoxicating beverage in a public house”.

“You do get used to the lingo.”