We pay his rent, mobile phone bills and travel costs. Taxpayers also cover the price of his internet access, job training courses and pay him an allowance. All in return for his terrorist "expertise".
Saajid Muhammad Badat, the 33-year-old son of Malawian immigrants, is Britain's first al-Qaeda supergrass. Jailed for 13 years in 2005, for conspiracy to destroy aircraft along with shoe- bomber Richard Reid, Badat's sentence was cut by two years in 2010 at a secret hearing in return for information. While Reid serves a life sentence at the Supermax in Colorado, Badat has been given considerable financial help in starting a new life. Presumably, the job courses the Metropolitan Police organised for him will enable him to become a PE teacher, which is his latest goal.
Badat's relatively light initial sentence reflected the fact that he abandoned his suicide mission, and flew home still wearing his exploding shoes. He subsequently hid the explosives in a black sock and the detonators in a case under his bed. These were discovered when he was arrested in late 2003. He said: "I know I've done wrong but I want to help the police now." He also added that he wanted to restore "calm" to his dangerous life.
Badat has undergone 45 hours of debriefing sessions, during which he displayed what prosecutors call "extraordinary mental abilities". The smart youth from Gloucester had trained as a bomber in al-Qaeda camps in Afghanistan, and was sufficiently well regarded to have one-on-one sessions with Khalid Sheikh Mohammed and Osama bin Laden - who explained to him that the strategy of blowing up aircraft was like breaking a link in the entire "chain" of the US economy.
Badat provided information useful to unravelling up to 18 terrorist conspiracies. However, he is still wanted under indictment in the US for his attempts at shoe-bombing, and so is currently testifying via video link to a court in Brooklyn. Here, a Bosnian-born US citizen Adis Medunjanin is on trial for conspiring with two others to bomb the New York subway with 7/7-style backpack bombs on the eighth anniversary of the September 11 atrocity. The imminence of this trial led the CPS to reveal their secret deal with Badat, which was also covered by a broad injunction. He is also likely to be a star witness when the so-called architect of 9/11, Khalid Sheikh Mohammed, goes on trial in Guantánamo Bay this autumn.
Badat's "arrangement" is one of 158 such deals concluded between prosecutors and informants since the Serious Organised Crime and Police Act of 2006. Eighteen people were granted either blanket or partial immunity and, in most of the other cases, any guilty pleas resulted in substantial sentence reductions.
The chequered history of informants and supergrasses highlights the strengths and weaknesses of relying on what some call "paid perjurers". The authorities, though, would argue that turncoats are one of the best ways of fracturing and destroying terrorist or criminal organisations, while publicly advertising exit routes for people involved in such activity. So can they be an effective new weapon in the war on terror?
Few will remember the name of Britain's first supergrass. Derek "Bertie" Smalls was a career armed robber who, in return for written immunity from the DPP, testified against 21 associates who were jailed for a total of 308 years. Smalls died peacefully in Croydon in 2005, despite his perilous midlife change of occupation.
Smalls was the trailblazer of a phenomenon that took off in the fight against London mobsters, before crossing the Irish Sea in the bigger struggle against Provo and Loyalist terrorists.
It was an international trend too, with the Italian authorities also using pentiti ("those who have repented") to good effect against the Mafia and the Red Brigades terrorists who turned Italy into an armed camp in the 1970s and 1980s. One of the Red Brigade grasses, Patrizio Peci, entitled his autobiography I, the Vile One, though his arrested comrades simply called him "that b------".
Widespread use of informers and supergrasses acknowledges the difficulty of inserting undercover agents into networks based on kinship or lifelong relationships. This becomes doubly difficult if, like Islamist terrorists, the culture is relatively alien to the authorities. Any self-respecting terrorist organisation does extensive background checks, with internal security services monitoring such things as runs of apparent operational bad luck, where the informant's hidden handlers have averted catastrophe. Meanwhile, the informant desperately attempts to continue as "normal".
Badat is relatively unusual in the sense that moral qualms joined cowardice in persuading him to abort his suicide mission. But even terrorists with long records of violence can be disillusioned by something particularly gruesome. Sean O'Callaghan, head of the IRA's Southern Command, had few qualms about shooting a police inspector in a bar, but he gradually wearied of the vicious sectarian mentality of senior colleagues.
One moment that tipped him into becoming a supergrass came while hiding in a safe house with senior IRA man Kevin McKenna. They were watching a television report about a policewoman killed in a bombing in Bangor. "Maybe she was pregnant and we got two for the price of one," opined McKenna. O'Callaghan then contacted a Garda Special Branch officer as a volunteer informer. He wrought havoc on IRA operations, before going on to testify against some seriously dangerous people.
Terrorists like Badat, Peci or O'Callaghan have sufficient independence of mind to see through the historical and self-romanticising myths that legitimise murder. More usually, supergrasses just grab opportunities to "talk and walk" in the hope of escaping the clutches of their organisation, or the criminal charges that no doubt await them. Lesser informants, meanwhile, often act just for money - and the thrill of knowing about and preventing future tragedies.
By definition, none of these are "nice" people. As one Italian head of the Anti-Mafia Commission said: "We do not find informants about the Mafia among nuns." But allowing someone to continue with a criminal career - be it in cigarette smuggling or VAT fraud - can have its benefits. Lucrative illicit dealings allow the informant to explain why they are so flush with cash - vital, especially in cultures that pay derisory wages, such as the £14 a month Badat got from al-Qaeda. In reality, of course, informers are also on a monthly retainer from their handlers.
Of course, these handlers have many delicate judgments to make. Terrorist organisations exist in an almost constant state of paranoia. When too many operations go wrong, it does not do for the informer to sweat or avoid eye contact. One mistake guarantees a prolonged encounter in some remote house equipped with a full bath, pliers, pokers, drills and blowtorches to race the imagination. It probably ends with the informer in a ditch with a bullet in his head, the fate of around 40 men who gave information from inside the IRA.
After investing considerable time and money in a grass, this bloody fate is the last thing the authorities want. But do they then let operations run their course, knowing that a judge or policeman will be killed, just to maintain their source's credibility and utility? Can protecting a supergrass ever justify sanctioning the occasional murder?
The most lethal informer the British probably ever had inside the IRA was Freddie Scappaticci, the barrel-chested head of its fearsome disciplinary "Nutting Squad". He embarked on his informant career in 1976 after a row with a senior republican led to a vicious punishment beating. After walking into an Army base, he was put on a retainer of £80,000 a year and shopped dozens of his colleagues, while continuing to execute other informers.
As every defence lawyer will claim, grasses and informers are not the world's most reliable witnesses. They have every incentive to make wild accusations, and are often motivated by personal grudges, like Scappaticci. Just such a case has recently resulted in the acquittal in Belfast of 12 out of 13 Loyalists accused of the murder of a rival paramilitary, Tommy English, shot lying on his sofa at Hallowe'en in 2000. Mr Justice Gillen described evidence from the "ruthless criminal and unflinching terrorists" Ian and Robert Stewart as "infected with lies", bringing to a close a 21-week trial that must have cost several millions. These alcoholic drug addicts had received three-year jail sentences for their role in killing English. They are free men now, thanks to their supergrass deal.
Saajid Muhammad Badat may prove highly useful in convicting extremely dangerous people. His gala performance will be in Camp Justice at Guantánamo, for he can directly connect Khalid Sheikh Mohammed with organising atrocities. If Badat can help convict the man said to be the mastermind of 9/11, no one can argue that the money - and the moral capital - invested in his grooming won't have been worth it.
Despite their uses, though, we should not idealise such figures, nor ignore the injustices that reliance on the honesty of criminals and terrorists sometimes entails. But supergrasses do afford a glimpse into the moral squalor of terrorist organisations, while their existence will surely shake the confidence of al-Qaeda cells and their operations. That is something in itself.