THE cost of an intensive three-week police video surveillance operation in Greenock which resulted in the seizure of just £35 worth of drugs will never be known.

A swoop carried out on the home of a suspected class A narcotics dealer — after teams of officers had gathered hours of footage over the course of 23 days — yielded just 0.18 grams of cocaine and 2.5 grams of cannabis.

Prosecutors pressed ahead with an indictment case against Pauline Smith, 47, who was acquitted by a jury in January on charges of supplying heroin and cocaine following just 36 minutes of deliberation.

Police Scotland said today it cannot provide accurate detail regarding the cost of the surveillance.

The operation involved officers filming activity at Smith’s front door flat on Brachelston Street from an unmarked van and providing live commentary to colleagues at another location.

Following a freedom of information request from the Telegraph, asking for the total cost of the operation and the number of officers and personnel hours involved, Police Scotland said ‘that information is not held’.

A force spokesperson added: “By way of explanation, the total costs relating to any investigation, both relating to the investigation itself and the number of hours involved, are difficult to quantify as the nature of policing means that officers are deployed to wherever their services are most required.

“Furthermore, the number of officers required throughout an investigation will fluctuate and officers involved in a particular investigation, or multiple investigations, can be redeployed to other duties at any time, dependant on their skillsets.”

The spokesperson added: “Police Scotland may keep limited records for investigations, which record overtime costs and non-pay costs.

“These costs do not provide an accurate reflection of the total number of hours spent on an investigation nor do they provide, for the reasons stated above, an accurate cost for an investigation.

“The costs do not include, for example, officer hours where that officer would have been on duty anyway and as such are not recorded as a specific expense to a particular investigation.”

Footage of the undercover operation, which was played in court, showed processions of people turning up at Smith’s door and calling through a letterbox.

Men described by police as being of ‘drug user appearance’ were heard to shout ‘Pauline’, another stated ‘She’s not got any’ and at one point three people were loitering outside.

The inside flap of her letterbox had the words ‘DO NOT SHOUT OR LOITER, NEIGHBOURS PHONE POLIS’ written in marker pen ink.

The Crown argued during the trial that there was ‘overwhelming and compelling’ circumstantial evidence in the case.

Defence lawyer Aidan Gallagher referred to a number of other people who had access to the flat, which also has a back door that was not monitored by the police.

Mr Gallagher said: “One might have thought that more research would have been done before setting up this surveillance.”

He told the jury: “A detective sergeant told this court that he saw a ‘transaction’ then recanted in the witness box. Is that credible evidence?

“The quantities of drugs recovered from the house were small, and little money [£65] as well, yet the Crown says that this supports the contention that Pauline Smith was involved in the supply of drugs.

“What are you left with? Assumptions and guesswork.”

The jury returned majority not proven verdicts on charges of being concerned in the supply of drugs between September 18 and October 10 2019.

Smith — who has a previous drugs conviction — was found unanimously guilty of simple possession of cocaine and cannabis and placed on supervision and drug treatment orders.