Isaac reached into the box herself and picked up a large gold locket in the shape of a heart. She passed it to James and said, ‘Check the inscription on the front.’

James read the words out loud. ‘To Mary. Happy Fortieth. Love Robert.’

‘And that’s not all, sir,’ Isaac said. She lowered the jewellery box lid and pointed to the words that were embossed on the leather.

To Mum. Happy Christmas. Love Charlotte xxx

‘Well now we know why O’Connor didn’t want us to search the house,’ James said. ‘I look forward to hearing what he has to say about this.’

By the time James returned home, adrenaline was fuelling every part of his body. He felt breathless, like he’d been running.

Annie was still in bed, but she wasn’t asleep. She told him she had no reason to get up so early so she was going to stay there.

‘Are you going to tell me why you had to rush out?’ she asked him.

He bent over the bed and kissed her on the forehead.

‘Can it wait until later? I need to have a shower and get going. I’ll put some food together for you before I go.’

‘Of course it can. And don’t worry about making me anything. With any luck I’ll be able to go back to sleep.’

‘An unmarked car will be outside all day and if you do decide to go out tell the officers. They’re not in uniform so they can follow you at a safe distance. I’m sure it’s an unnecessary precaution, but it’ll give me some peace of mind.’

He showered and dressed downstairs and was on his way to Kendal by 6 a.m. It was still dark and the roads were awash with snow and slush so he drove slowly and carefully, and used the handsfree device to phone Tanner to tell him about the development with the jewellery box. The DCI was already up and getting ready to head for the station himself.

‘This sounds like a game changer,’ he said. ‘If we’re going to formally interview him this morning, I’ll get onto it and make sure there’s a duty solicitor around.’

A fizz of excitement was running through James when he arrived at the station. Some team members were already in and so he was able to get things moving straight away.

The custody sergeant was told to prepare Kenneth O’Connor for the formal interview and James asked officers to dig up more information on the man. He wanted someone to talk to his former girlfriend and run a check on his bank and social media accounts.