The test purchasing operation began at a newsagent in Glasgow which was known to sell fake cigarettes - and I was going to attempt to make a purchase.

“Make sure you crumple the tenner before you put it on the counter,” said the former police officer leading the sting, “if the bank note looks too crisp they will get suspicious.”

We walked in and I asked for two packets of a well-known brand. The shopkeeper reached back to lift the cover of the display where cigarettes are stored.

“No, the £4 ones,” my companion said, forcefully. He immediately bent down to a storage area under the counter and produced two packets of fake fags with familiar branding.

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I put the crumpled bank note and the counter and the transaction was complete. It was that easy.

“Beginners’ luck,” the former police officer said as we left the shop, “It’s not always that simple.”

Glasgow Times: Former Met Police DCI Will Oà 	Reilly take the ET on a tour of Glasgow to uncover the extent of the cityà 	s illicit tobacco problems. ..

I discovered this for myself at another shop in a different part of the city.

When we went into the convenience store the shopkeeper was visibly shifty, sizing us up as we approached the counter.

I put a crumpled five pound note in front of him and again asked for two packets of cigarettes – this time we were after the cheaper products at £2.50 each, which are smuggled in.

He stared at the note, stared at me and eventually opened a drawer directly under the till which contained dozens of packets of illicit tobacco.

He took the money, put the cigarettes on the counter and immediately moved to the main area of the shop and attempted to cut us off at the door.

My companion blocked his path allowing me to leave, before following me out. The shopkeeper watched us walk away, then took a mobile phone out of his pocket and put it to his ear.

“He knows,” said the former police officer, “and he’ll be warning other traders.”

Glasgow Times: Former Met Police DCI Will Oà 	Reilly take the ET on a tour of Glasgow to uncover the extent of the cityà 	s illicit tobacco problems. ..

We decided to change the strategy and sought out the “baccy man” – a regular at a pub who sells illicit cigarettes from a plastic bag with the blessing of the bar staff who will often point them out.

In one city pub there was no attempt to hide his haul which was spilling out of a supermarket carrier bag by his side.

I stared at the cigarettes and he immediately gathered up the bag and drew it closer, but not before handing over a pouch of illicit rolling tobacco which he sells for half the value.

In a few hours we were able to but hundreds of pounds worth of counterfeit products in various locations throughout the city, proving there is a thriving trade in Glasgow.