APPEAL COURT, HIGH COURT OF JUSTICIARY
 HCJAC 95
Lord Justice Clerk
OPINION OF THE COURT
delivered by LORD CARLOWAY, the LORD JUSTICE CLERK
in the Appeal under section 74 of the Criminal Procedure (Scotland) Act 1995
HER MAJESTY’S ADVOCATE
Appellant: Mullan; Faculty Services Ltd (for Blantyre Criminal Lawyers, Blantyre)
Respondent: Erroch AD; the Crown Agent
1 July 2015
 This is an appeal from the determination of an objection, raised by way of preliminary issue, to the admissibility of evidence obtained during a search carried out under section 23 of the Misuse of Drugs Act 1971. The search was of a grey Fiat Punto, which had been stopped on the M90 near to Kinfauns. The appellant was the driver and sole occupant. The search, which was carried out later at a police office, revealed 500g of diamorphine hidden in the central console.
 The stopping of the appellant’s car formed part of a large scale police operation, investigating the suspected supply of Class A controlled drugs in Central Scotland. The police were of the view that the drugs were being distributed to couriers from the premises of a waste disposal company in Shotts.
 The judge at first instance, having heard evidence, reports that the police operation involved a surveillance team and an investigating team. DS McKay was in charge of the investigating team. The officers were linked in a radio talk group. The surveillance operations were reported to the group.
 The investigating team were privy to intelligence about the Fiat Punto, the identity of its driver, its predicted route along the M90, and its intended destination in Dundee. They had information that it was carrying controlled drugs. DS McKay accordingly telephoned the Perth Roads Policing Department and spoke with PC Gillies. He told PC Gillies that there was active on-going surveillance on the car. He gave PC Gillies details of the car and its driver and said that it was believed to be en route to Dundee. He said that he would like the car stopped before it arrived in Dundee. He told him that he had information that there were controlled drugs in the car. He did not discuss the details of the intelligence with him, but, as PC Gillies understood it, DS McKay knew that there were controlled drugs in the car.
 PC Gillies took up a position at a point where the M90 becomes the A90 on the way to Dundee. He and a colleague stopped the car. PC Gillies told the appellant that he was being detained in terms of section 23. He had detained the appellant because, as he put it, he had been given information that there were controlled drugs in the car and he felt it was proportionate to detain the appellant for the purposes of a search. The investigating team officers arrived immediately thereafter and also told the appellant that he was being detained under section 23. They were told that that had already been done.
 It was submitted to the judge by the Crown that PC Gillies had effected a valid detention, having had reasonable grounds to suspect. In any event, a second detention had been carried out immediately afterwards by officers who had undoubtedly had reasonable grounds. Since there was no prejudice to the appellant or unfairness, any irregularity ought to be excused. The appellant contended that there had been no reasonable grounds to suspect on the part of PC Gillies, as distinct from the investigating officers, and that the purported detention was unlawful. Nothing done thereafter repaired that irregularity.
 The trial judge distinguished the circumstances from McGaughey v HM Advocate 2014 SCCR 11. In his view, McGaughey had been concerned with a mere instruction to detain. In contrast, this case was that:
“PC Gillies had enough information from the [investigating] team to form his own suspicion, … he did form his own suspicion and …, applying both the subjective and objective tests referred to in the case law, he personally had ‘reasonable grounds to suspect’ and therefore a lawful basis for effecting the detention. … if PC Gillies did not effect a lawful detention, any irregularity ought to be excused having regard to all the circumstances. … the irregularities in Lawrie [v Muir 1950 JC 19] and in McGovern [v HM Advocate 1950 JC 33] were not excused but … the principles set out in those cases justify excusal in the present case.”
The trial judge accordingly repelled the objection.
 The submission for the appellant essentially repeated that which had been presented to the judge at first instance. In particular, emphasis was placed on the circumstances of McGaughey v HM Advocate ( supra) and HM Advocate v B  HCJ 71 . There was no good reason for the investigating officers not to have given such information to the detaining officer as would have allowed him to have formed his own conclusion on whether reasonable grounds to suspect existed. Officers who sought to exercise a statutory authority to detain persons ought to know the precise limits of that authority. They should be held to exceed these limits at their peril (see Lawrie v Muir ( supra) and McGovern v HM Advocate ( supra)). The fact that investigating officers arrived shortly after the detention did not excuse the irregularity.
 The Crown accepted that, on the strength of McGaughey v HM Advocate ( supra), the detention was irregular, but maintained that the irregularity ought to be excused in all the circumstances.
 The issue is whether PC Gillies was in possession of sufficient information to provide him with reasonable grounds to suspect that there were controlled drugs in the car. In this area of the law, each case will depend upon its own particular facts and circumstances ( McKenzie v Murphy 2015 SCCR 88, Lord Malcolm at para ). It is true that PC Gillies was following instructions received from DS McKay. However, the judge at first instance has found in fact that PC Gillies had sufficient information to provide him personally with reasonable grounds to suspect. PC Gillies had been told by a detective officer engaged in an active, on-going surveillance operation that he (the officer) was aware that the car was carrying drugs. That was sufficient in the context of this type of case for a reasonable suspicion to be formed, without the need for further interrogation of the source officer.
 The Court in McKenzie v Murphy ( supra) explained that the ratio of McGaughey v HM Advocate 2014 SCCR 11 was that a reasonable suspicion could not be created in the mind of a detaining officer merely on the basis of an instruction to detain from a fellow officer. In McGaughey, all that the detaining officer had was information conveyed to him second hand that the Scottish Crime and Drug Enforcement Agency thought that a particular car might be carrying drugs. In this case, in contrast, the detaining officer had information conveyed to him directly from a detective engaged in an active, on-going surveillance operation. That information was that there were drugs in the car; and not merely that DS McKay suspected that there might be. Following Lord Steyn’s dictum in O’Hara v The Chief Constable of the RUC  AC 286, Lord Malcolm in McKenzie confirmed (in para ) that it was not enough for a superior officer, who had reasonable suspicion, to order a detention by another officer. The detaining officer must have his own reasonable suspicion. However, it was stressed that that suspicion could come from hearsay information emanating from another officer. That is the position here.
 In these circumstances it is not necessary to go on to consider whether any irregularity in the search ought to be excused. The appeal against the decision at first instance is refused.