His life had changed irrevocably in 1980. His mother and father were killed in a crash on a German autobahn and John had been sent to live with his Aunt and Uncle in Kent. A substantial amount of money was bequeathed to him in trust, and it was put to good use. He was provided with a first-class private education and, after passing the rigorous entrance examination, he was sent up to Eton for the Autumn term in 1981. His career there was not successful and, thanks to an incident that MI5 had not been able to confirm (although they suspected it involved gambling), Milton was expelled. There was a period of home tutoring before he was accepted at his father’s old school, Fettes. He stayed there until he was sixteen and then took a place at Cambridge to read law.

He was involved in the OTC and it had been no surprise to anyone when, in 1989, he ignored the offer of a pupilage at the Bar to enlist in the Royal Green Jackets. He was posted to the Rifle Depot, in Winchester, and then sent to Gibraltar as part of his first operational posting. He served in South Armagh, where, as a newly promoted Lance Corporal, he killed for the first time during a firefight with the Provisional Irish Republican Army. In 1997, after spending eight years with the Green Jackets, he decided to attempt SAS selection. The process was renowned for being brutally difficult but he passed, easily. While serving with Air Troop, B Squadron, 22 SAS for ten years, Milton worked on both covert and overt operations worldwide, including counter terrorism and drug operations in the Middle East and Far East, South and Central America and Northern Ireland. He trained as a specialist in counter terrorism, prime target elimination, demolitions, weapons, tactics, covert surveillance roles, information gathering in hostile environments and VIP protection. He worked on cooperative operations with police forces, prison services, anti-drug forces and Western backed guerrilla movements as well as on conventional special operations.

Control turned through to the pages dedicated to Milton’s service during the First Gulf War. He had been dropped behind Saddam’s lines to take out the Scuds he was using to launch rockets into Israel. His patrol had eventually been compromised, the men fleeing on foot towards Syria. Three were killed and the others were captured. Milton was held for six weeks and tortured throughout. By the time they forced their escape in a firefight during which three of the others were killed he was suffering from nerve damage to both hands, a dislocated shoulder, kidney and liver damage, and had contracted hepatitis B.

The Distinguished Conduct Medal he received on his return to London, together with the Military Medal that he won during a patrol in Northern Ireland, made Milton the British Army’s most highly decorated serving soldier when Control decided that he was the perfect replacement for Number Seven, who had been killed while on operations in China. He made the pitch himself. It was a persuasive offer, and Milton had accepted immediately.

Control put the history aside and turned back to contemporary papers. Milton’s recent yearly assessment had seen a significant dip in results and, as he turned back through the years, he noticed a trend that had remained hidden until then. The assessments were intense, and combined a rigorous physical examination, marksmanship tests and a psychological evaluation. Milton’s performance in all three elements had been in decline over the last three years. The drop was steepest this year, but it was not isolated. He chided himself for missing it. His continued success in the field had blinded him. He was so good at his job that the suggestion that he might not have been infallible was ridiculous. Now, as he examined his file with the benefit of hindsight, he saw that he had missed a series of indicators.

His physical examinations returned strong results. He was fit, with the cardiovascular profile of a man fifteen years younger. He made it his habit to run a marathon every year and the times had been noted and added to the file; he had never finished the course in more than three and a half hours. Nevertheless, he had suffered a series of injuries in the field that had exerted a toll on his body. The damage inflicted during his incarceration in Iraq had been severe, but there had been other incidents. Since joining Group Fifteen he had been shot twice, stabbed in the leg and shoulder and had broken more than a dozen bones. He reported the usual aches and pains but the physician suggested that he was being stoic for the benefit of the examination, and that it was likely that he was in mild to moderate pain most of the time. Blood tests detected the beginning of mild arthritis in his joints, a condition for which there was a familial history. He took a cocktail of drugs: gabapentin for his nerve damage and oxycodone for general pain relief.

Control relit his cigar and picked up his psychological assessment. He stood to stretch his legs and read the report next to the window. As he skimmed through the pages he realised that missing the warning signs contained within had been his most egregious error. The psychiatrist noted that Milton had complained of sleeplessness and that he had been prescribed promathazine to combat it. There had been a discussion about reasons behind the problem but Milton had become agitated and then angry, refusing to accept that it was anything other than an inability to quieten a busy mind. The psychiatrist suggested that Milton’s naturally melancholic temperament indicated mild depression and that he seemed to have become introspective and doubting. The report concluded with the recommendation that he be monitored on a more regular basis. Control had ignored it.

Damn it.

Milton was a valuable asset and he had wilfully ignored the warning signs. He did not want to admit that there might be a problem and his inaction had allowed it to metastasise.

He put the files back into the storage crate and lit a second cigar. There came a knock at the door.

“Come in,” he called.

Christopher Callan came into the office. He was Number Twelve: the most recent recruit to the Group. He had been transferred from the Special Boat Service after a career every bit as glittering as Milton’s had been. He was tall and slender and impeccably dressed. His jacket was two-buttoned, cut from nine-ounce cloth. The pockets were straight and the lining was simple and understated. There was a telltale faint bulge beneath his left armpit where he wore his shoulder holster. He did not wear a tie. The trousers were classically cut, falling down to the back of his shoe. He was strikingly handsome although his head was round and small, supported by a muscular neck. His scalp was covered with tight blond curls that were almost white, reminding Control of the classical hair of the statues of da Vinci. The curls were thickly pressed against each other and against the skull. His skin was a pristine white and his grooming immaculate. There was a cruelty to his thin-lipped mouth and the implacability that veiled those pale blue eyes seemed to infect the whole face. It was, Control reflected with a moment of mild revulsion, as if someone had taken a china doll and painted its face to frighten.

“You wanted to see me, sir?” he said.

“Yes, Callan. Take a seat.” He inhaled deeply, taking the smoke all the way back into his throat, then blowing it out. “We’ve got a bit of a problem. It’s one of the other agents — do you know Number One?”

“Only by reputation.”

“You’ve never worked with him, though?”

“No, sir. Why?”

“Afraid he’s started to behave a little erratically. I want you to find out everything you can about him — where he’s living, what he does with his time, who he’s seeing. Everything you can.”

“Yes, sir. Anything else?”

“No. Start immediately, please.”