8.  On 28 February 1995 Detective Inspector Mann (D.I. Mann), received information that an armed robbery of a Securicor Ltd cash-collection van was going to be committed on or around 2 March 1995 by the first applicant and B. at one of several possible locations. The police knew where B. lived and began visual surveillance of those same premises the same day. D.I. Mann learnt that B. was suspected of being a drug dealer and that surveillance operations mounted against B. in the past had proved unsuccessful because they had been compromised. It was therefore concluded that B. was “surveillance-conscious”. B. was suspected of being responsible for the shooting of a police officer with a shotgun in the course of a robbery. This was something that all the officers, and particularly the Chief Constable, were aware of when the police operation was being planned. 9.  No robbery took place on 2 March 1995. By 3 March 1995, however, the police had received further information that the robbery was to take place “somewhere” on 9 March 1995. Further information as to the location or target of the proposed robbery could not be obtained on 3 March 1995. In order to obtain further details about the proposed robbery, D.I. Mann prepared a report for the Chief Constable in support of an application for authorisation to install a covert listening device in B.’s flat. Some of the contents of this report were the subject of a successful application for non-disclosure by the Crown on the ground that serious damage would be caused to the public interest were they to be made public. 10.  The use of covert listening devices was governed by the “Guidelines on the Use of Equipment in Police Surveillance Operations” issued by the Home Office in 1984 (“the Guidelines”). On 3 March 1995 the Chief Constable decided that the use of such a device was justified under the Guidelines but would not authorise its use until he was satisfied that its installation was feasible. Reconnaissance during the night of 3/4 March established that it was feasible. 11.  On 4 March 1995 the Chief Constable gave oral authorisation to proceed with its use. However, he did not provide written confirmation as required by the Guidelines because he was on annual leave, so he gave the authority by telephone from home. The Chief Constable stated that the use of the device was to be reviewed on a daily basis. He said that he had asked the Deputy Chief Constable to look after the written formalities and to ensure, inter alia, that there was written confirmation of the message that the installation of the device was feasible. He did not receive this confirmation until 8 March. On 8 March 1995 the Deputy Chief Constable gave “retrospective” written authorisation for use of the listening device. 12.  On 4 March a covert listening device was therefore installed in a sofa in B.’s flat before the Deputy Chief Constable had confirmed the authorisation in writing. Conversations between B. and others in B.’s living room were monitored and recorded until 15 March 1995. 13.  On 14 March 1995 the police made a request to BT (British Telecommunications PLC) for itemised billing in relation to the telephone number of B. at his flat for the period from 1 January 1995 to the date of the request. The data-protection form was countersigned by a police superintendent in line with BT’s requirements, stating that the information was necessary to assist in the identification of members of a team of suspected armed robbers. While the request was originally made in an effort to identify the unknown third person in the conspiracy (now known to have been the second applicant), the data was also used later in court to corroborate the times and dates recorded by the officers in respect of the covert listening device in the flat. 14.  On 15 March 1995 B. and others who were with him in his home discovered the listening device and abandoned the premises. The robbery did not take place. The police had been continuing their visual surveillance of the premises, taking photographs and video footage whilst the audio surveillance was in progress. The applicants were identified by various officers going in and out of the flat and observed on some occasions to be carrying various hold-alls. The police had also been keeping watch on a cache in a rural location and observed the first applicant collecting an item from this location on the evening of 15 March 1995. An officer had earlier inspected the hidden item, which he stated he could tell through the plastic bag was a revolver. It appeared that the vehicle which the first applicant used for transport that evening was a stolen vehicle in which he was subsequently arrested. 15.  On 16 March 1995 the applicants were arrested in the stolen Vauxhall car. In the boot of the vehicle were found two hold-alls containing, inter alia, two black balaclavas, five black plastic cable ties, two pairs of leather gloves and two army kitbags. Following legal advice, the applicants declined to comment during interview and refused to provide speech samples to the police. The police obtained a search warrant for the flat and searched it. Fingerprints of the applicants were found, as well as items such as a pair of overalls and a third balaclava. Three vehicles were recovered and examined. The items retained included balaclavas, hold-alls, overalls and a broken petrol cap. 16.  As they wished to obtain speech samples to compare with the tapes, the police applied for authorisation to install covert listening devices in the cells being used by the applicants and to attach covert listening devices to the police officers who were to be present when the applicants were charged and when their antecedents were examined. Written authorisation was given by the Chief Constable in accordance with the Home Office Guidelines. Samples of the applicants’ speech were recorded without their knowledge or permission. In the case of the second applicant, the conversations that were recorded included, on one occasion, the second applicant taking advice from his solicitor. The Government state that, when the police officer realised what the conversation was about, it was not listened to. That recording was not adduced in evidence at trial. 17.  The voice samples of the applicants were sent to an expert who compared them with the voices on the taped recordings of conversations held in B.’s home between 4 and 15 March. The expert concluded that it was “likely” that the first applicant’s voice featured on the taped recordings and that it was “very likely” that the second applicant’s voice featured on them. 18.  B. and the applicants were charged with conspiracy to rob Securicor Ltd of monies. B. pleaded guilty in view of the House of Lords decision in R. v. Khan ([1996] 3 All England Law Reports 289). The House of Lords held in that case that relevant evidence was admissible notwithstanding that it had been obtained by unlawful means (for example, trespass). The applicants, however, challenged the admissibility of the evidence derived from the use of the covert listening devices at B.’s home on two grounds.
(a)  The Chief Constable should not have authorised the use of a covert listening device at B.’s premises because other forms of investigation had not been tried and failed as required by paragraph 4 (b) of the Guidelines, with the result that it would be unfair to admit evidence which ought never to have been obtained.
(b)  The covert listening device had been installed and used before written confirmation of the Chief Constable’s authorisation had been received and there was no specific permission for the recordings obtained from the device to be used in evidence.
Before the jury was sworn in at the trial, Judge Brodrick heard evidence by means of a voir dire (submissions on a point of law in the absence of the jury) on matters relating to the admissibility of the challenged evidence. The prosecution conceded that the relevant evidence had been obtained by unlawful means, namely trespass. During this procedure the prosecution claimed that the public interest was likely to be damaged if certain disclosures were made and certain evidence given, in other words claiming public interest immunity. The prosecution argued that the test of admissibility was relevance. The defence argued that the judge had the discretion to exclude the evidence under section 78 of the Police and Criminal Evidence Act 1984 (PACE), and that he should do so because the Chief Constable had failed to abide by the Guidelines. 19.  Judge Brodrick decided that some documents, including D.I. Mann’s report, which led to the Chief Constable’s decision to authorise the use and installation of a covert listening device in B.’s flat, were to be withheld from the applicants and their lawyers. The judge kept under review the non-disclosure during the proceedings and at one point some disclosure was made, although not D.I. Mann’s report in its entirety. D.I. Mann also declined to answer questions put to him in cross-examination by defence counsel on the ground that it might reveal sensitive material. Judge Brodrick asked defence counsel whether they wanted him to put the unanswered questions to D.I. Mann under oath, in chambers, and they agreed. The judge proceeded to put the questions to D.I. Mann in private in the absence of the applicants and their lawyers. He heard evidence from D.I. Mann concerning the ability of the police to “control” B. in order to install the device in the flat, which the defence asserted indicated that normal methods of surveillance would have been possible. He also heard D.I. Mann concerning the arrangements made and put into effect for this period. The answers to those questions were not divulged, the judge indicating in open court that the benefit to the defence from the answers given was slight, if any at all, while the damage to the public interest if the answers were made public would be great. Accordingly, he held that D.I. Mann was entitled on public immunity grounds to refuse to answer those questions. 20.  Judge Brodrick rejected the applicants’ challenge to the admissibility of the evidence derived from the covert listening devices in B’s flat. In reaching his decision, Judge Brodrick stated:
“61.  It follows that I must apply the test set out in section 78 on the basis that this was a properly authorised decision to install the device and that the police were justified in continuing to use it up to the moment when it was discovered. At most there were one or possibly two breaches of procedure, but neither, in my judgment, could be described as either significant or substantial. It is conceded by the Crown that the installation of the device amounted to a civil trespass. In addition it was a serious invasion of privacy in circumstances in which those concerned would have expected their conversations to be private. 62.  I was invited to take into account, and I do, that the installation of the device may well amount to an invasion of the general right to privacy under Article 8 [of the Convention]. It is not for me to determine whether there has, in fact, been a breach of Article 8, but in weighing this point I must bear in mind that it is at least arguable that the interference in the present case could be justified on one or more of the grounds set out in Article 8 § 2. In those circumstances I cannot see any reason for concluding that the possible breach of Article 8 was either substantial or significant. 63.  I was also invited to consider whether the admission of this evidence and the difficulties faced by the Defence in seeking to test the validity of the Chief Constable’s decision breached Article 6 of the Convention ... I am satisfied beyond reasonable doubt that to the extent that there has been a breach of Article 6 it has not in fact deprived these Defendants of the right to a fair trial.” 21.  The applicants also challenged the admissibility of evidence derived from the use of covert listening devices attached to the officers charging them and dealing with their antecedents. Judge Brodrick stated:
“75.  ... it does not seem to me to be right to attach great weight to the unfair way in which the control tapes were obtained. The fact that they provide relevant evidence, in the sense that they are a reliable sample of speech, which can be clearly attributed to each of these Defendants, weighs more heavily in my judgment. On balance therefore I am satisfied that the admission of the control tapes would not have such an adverse effect on the fairness of the proceedings that I ought to exclude them.” 22.  The police submitted statements from those officers who had conducted the audio and visual surveillance of the flat, and the searches of the flat and the recovered vehicles. There was also evidence from officers who had been keeping watch on a cache. One officer stated that the item hidden under a tree was in fact a revolver. The first applicant was seen collecting this item on the evening of 15 March 1995. 23.  On 9 August 1996 the applicants were convicted of conspiracy to commit armed robbery and were sentenced to fifteen years’ imprisonment. They applied to the Court of Appeal for leave to appeal on grounds relating to the judge’s rulings to admit taped evidence. They did not challenge the judge’s decisions with respect to non-disclosure of certain evidence on public interest immunity grounds. Their applications were refused on 12 November 1996, a single judge finding that the judge’s exercise of his discretion to admit evidence did not give rise to an arguable ground of appeal. Notification of the refusal was sent to them on 10 and 20 December 1996 respectively. It does not appear that the applicants made any complaints to the Police Complaints Authority in respect of the covert listening devices.