‘When did you know it was him?’

‘I think it was when he sold up the business, and bought some warehouse space somewhere to set up a fish wholesaler. I thought, “I bet poor Jane is in the freezer”.’

‘Weren’t you ever tempted to tell the police?’

‘And throw my family to the wolves? Not on your nellie. No, the nearest I got was when Harold died in 2002. Graeme came to see me, and said he would sort out the sale of all his fish stuff, which had lain unused in some warehouse somewhere since he got ill and closed down the wholesaler. Hello, I thought, what’s going on here. That Graeme never offered to do anything for nothing. Even then he was a smarmy one, trying his charm to get round me.’

‘Did you have an address for this wholesale business?’

‘No. I’d lost interest. I think it was somewhere in Surrey. But as they always say, tell me no secrets and I’ll tell you no lies.’

After he had finished the interview Perry picked up his notes and drove off towards his home in Woking. The datasticks now contained photographs of all the historic case records, witness statements, interview records and so on from 1982 that he had picked up from the archives in Tooting, and now this crucial evidence on tape from the grandmother. He emailed off a digital copy of the interview to DC Rainy Macintosh and DCS Rajinder Otara.

He wasn’t going to go straight home, though. His sanity depended on not having to confront Mel again. Last night he had slept in the car in a country lane, and if necessary he would do it again tonight. He could keep the laptop charged from the USB port in the car, and could pretty much do what he needed to do.

Perry parked his unmarked VW Polo by the site office of the Shepherds’ Rest estate and set the dash cam so it would capture all the vehicle movements through this, the only entrance to the estate. If a black Range Rover passed, he would spot it.

He rang Rainy Macintosh, who had been researching all the British suppliers and distributors of ultra-low temperature freezers. ‘Hiya boss,’ she said with her usual level of cheerful Glaswegian insubordination. ‘Still at work on a Saturday evening?’

‘Not exactly,’ he replied. Just planning revenge against my wife’s lover, as one does.

She told him that most of the freezers were used in medicine, mainly designed for small samples. They would generally be too small to hold a human body. They were also pretty expensive.

‘I’ve been on to the four biggest suppliers, and they do keep customer lists because of a servicing requirement. Most of them are companies or universities or research institutes.’

‘What about the exceptions?’ Perry asked.

‘Aye, if you go on eBay or Alibaba, there are all sorts of manufacturers you can deal with directly. If it’s a Japanese tuna freezer, or walk-in freezer room, you can get one made to order. These are going to be much harder to trace so—’