‘At the time of death obviously not. There was no trace of foetal tissue, and the uterus was of a normal weight. But the more vexing question is had she ever been pregnant, and on the balance of probability, assuming no false signal from the beta HCG, I would say yes. That of course is a provisional conclusion.’

Perry thanked him and hung up. Speaking to a real scientist was refreshing. The man’s mind was clearly as sharp as a scalpel. The detective knew he needed more evidence, and turned to an experienced-looking desk sergeant to help him. ‘In 1982, where might a young girl have dropped off an unwanted baby in this neck of the woods?’

The sergeant, a thick necked and grizzled officer narrowed his eyes and said. ‘You’d be best off looking for press coverage. Abandoned babies were news. Try to go via the NHS, and you’ll get tangled up in privacy and data protection issues.’ He logged Perry into the database of the local newspapers from that time. Nothing came up about abandoned newborns a year either side of the date of the crime.

The detective inspector leaned back in his seat with his hands behind his head and his face creased in concentration. What other possible lines of analysis could he undertake? If the Garrisons had adopted a child born to their niece, there should be school records. Again he asked for the help of the sergeant. Fortunately, they were looking in the days before ‘choice’ became the key word in education, so generally speaking most kids went to the nearest infant and junior schools. The two of them put in calls to all the relevant school offices, but considering it was after five o’clock, they knew they would get no answers before the following Monday.

One idea kept circulating in Perry’s head. That the fishmonger had first impregnated his own niece, and had adopted the resulting baby. Someone in Jane’s family would have known she was pregnant, surely. He conceded it was going to be very hard to prove now, but clearly if he was right, any family cover-up would be a huge issue for the police to have missed. The next thing was to try to find records for the child.

Perry picked up his coat and emerged into the grey drizzly car park, the drone of traffic all around. He contemplated a long and tedious drive through the rush-hour traffic until he got to Woking, and his own not-very-welcoming home. Work, the best part of the week, was now over. It was Friday night, and all he had to look forward to was the prospect of emotional hand-to-hand combat with his estranged wife, a woman who had the verbal equivalent of a black belt in karate. He dreaded it. If there was anywhere else he could have gone, he would have. He wasn’t due on shift, but he’d go back in to the office first thing tomorrow anyway.

It was Friday afternoon before Gillard was allowed to return home and collect some clothing. CSI chief Yaz Quoroshi was just leaving, the last of the crime scene vans just reversing out of his drive as Gillard drove into the cul-de-sac. They greeted each other through open vehicle windows. ‘What have you discovered?’ Gillard asked.