If the house they pulled up outside on Nan Clark’s Lane was any indication of status, Mary Locke had managed to shelter from the storm of the recession in relative comfort. They had only left the M1 a few minutes ago, but the impressive detached residence a short hop from Edgware had a secluded, exclusive feel to it. The dark wooden gates covering the driveway were closed, but the roof of a pristine white Range Rover poked over the top of them. The house itself looked perfectly symmetrical; a pair of sandstone effect columns flanked the doorway on either side, like soldiers standing to attention, with the lintel made from the same material. The matching sets of windows, three up and three down, on either side of the front doorway, acted like mirrors rather than portals into the interior, although Porter wagered that Mary Locke herself had never had to stoop to polishing them to get that shine.

He had toyed with calling ahead to check somebody was in, but that would open up a line of questioning he would rather pursue face-to-face. Porter pulled up on the opposite side of the narrow private road they’d driven up to get there, and motioned for Styles to stay in the car while he went to push the intercom button on the gate; no sense them both getting out unless they knew they’d be staying a while.

He pushed the button and held it for a three count, then took a step back. There was no immediate sign of life from inside. A double garage sat off to the left with both doors closed, no doubt harbouring an equally expensive vehicle to rival the Range Rover. There was a split second of static from the intercom, followed by a woman’s voice.

‘Yes, who’s there, please?’

‘Mrs Locke?’ said Porter.

‘Yes, speaking. Who is this, please?’ she repeated her question politely.

‘Mrs Locke, my name is Detective Inspector Jake Porter with the Met Police. I’m here with my partner, Detective Sergeant Nick Styles. We’d like to ask you a few questions about a matter we’re investigating, if you can spare us a couple of minutes, please?’

There couldn’t have been more than two or three seconds of silence before the burst of static again, but the time oozed past like treacle, making it seem like double figures. Was she thinking of an excuse not to let them in, or just a little flustered to have police on the doorstep? Whatever would the neighbours say? Porter reminded himself they were in an unmarked car, and he hadn’t been in uniform for many years now, so the secret of their visit was safe from prying eyes for now.

‘Can I ask what it’s about, Detective?’

‘It would really be a lot easier to explain if we came in, Mrs Locke,’ said Porter.

Another brief pause. ‘Do you have any identification with you, please, Detective?’