An hour later, with the formal debrief concluded, I headed back to the negotiation control room. No further mention was made of Superintendent Mellor’s decision to use a rapid entry while negotiation was still ongoing. The advice from John Southern was timely and went some way to making me feel better about what had happened.

I was hoping to find Peter Hesp from the Technical Support Unit before he finished packing up ready to head back to Scotland Yard. I was in luck. He was sealing the last of his kit into plastic crates as I walked through the door.

‘Cometh the man, cometh the hour eh, Finlay?’ Peter teased.

I glanced around. We were alone. ‘At least we got a result and nobody was hurt,’ I said.

‘Not much of a result for that poor PC though. And I reckon the girl he was holding will have a few nightmares after today.’

‘You were listening in then?’

‘Always. In case there’s a comms issue, that kind of thing.’ He started stacking the crates, ready for loading into his van, I assumed.

‘So, how did I do?’ I asked.

‘Pretty good, I reckon, especially as it was your first call-out. And from the thumbs-up and looks that went around the office, I reckon the old hands approved.’

‘Did you hear the argument between the divisional lads and the CIB Superintendent?’ I was curious, and it was useful small talk as I worked out if Peter was likely to be receptive to my real reason for seeking him out.

‘Nah,’ he said. ‘That happened offline, in an upstairs office. Got pretty heated from what I heard.’

‘That’s what I was told too.’ I reached in my pocket and gently took hold of the device from Kevin’s house. ‘Peter,’ I asked. ‘I wonder if I could beg a favour?’

He peered towards me, a look of curiosity on his face which was soon replaced by a smile. ‘If you want me to put a bug in that Superintendent’s office, forget it,’ he said, grinning from ear to ear.

‘Nothing like that. But I do need you to give me some private advice, something I’d prefer was just between us.’

The smile turned to a frown. ‘I work in a world of secrecy, Mr Finlay. You’d probably be surprised, maybe horrified, to know the kind of things that I keep shtum about.’

I held out my hand, the tiny device and attached wire now clear for him to see.

He stepped forwards, reached into his trouser pocket and pulled out a grubby pair of spectacles. After wiping them clean on a handkerchief that looked like it doubled in function as a rag used to check the oil on his car, he slipped them over his nose and leaned over my open hand.

‘May I?’ he held out his hand, indicating that I should pass the device to him. I placed it carefully on his palm.

He studied it for a moment, turning it over, seemingly looking for an identifying mark. ‘Where did you get this?’ he asked, finally.

I rubbed at the stubble on my chin. Peter then raised a hand, his smile enigmatic. He was effectively calling a halt to any need for me to lie. ‘No worries,’ he said. ‘I should know better than to ask. But, I would be interested to know. It’s a device of the kind that our budget normally doesn’t run to. State of the art, great range and uses the power of the mains system so it can last almost indefinitely.’

‘It’s a listening device?’ I demanded.

‘A Bowland Technics A700X.’

‘That’s pretty specific.’

‘It should be. I put in a requisition for a few of these babies not too long ago. It was turned down on account of their cost.’

‘Expensive?’

‘Very. So much so that they aren’t commonly used. You can get much cheaper products that do the same job, well nearly. Like I said, these have a great range, fantastic sound quality and they don’t rely on battery power.’

‘So whoever planted it … they’re not from the Met?’

‘I wouldn’t have thought so.’ Peter shrugged and shook his head. ‘We’ve had similar devices on trial occasionally but, to the best of my knowledge, only the Arabs and the Yanks use these. Not even our intelligence services can justify the cost.’

‘Intelligence services? You mean it isn’t a police-used device?’

‘Smart money would be on the CIA or similar.’ He hesitated for a moment, frowning. ‘That said, there were a few sent out as samples to MI5 and Six. But like I said, after field tests, I think they decided not to buy them. The Met may have looked at them but we don’t use them.’

‘So … say for argument’s sake it was found in a house here in the capital, it’s possible it might be someone within our own Security Services who planted it?’

He smirked. ‘You’d have to ask them, Finlay. It has a serial number but you’ll need better eyes than mine to read it. Trouble is, as soon as you start asking where it came from, sure as eggs are eggs the department that placed it will be tipped off.’

‘How come?’

‘MI5 operate like us in many ways. They have stores, logistics, admin … just like any large organisation.’ He handed the tiny device back to me. ‘Expensive stuff like this has to be accounted for. There’ll be a record of who it’s booked out to … or there should be.’

‘Unless someone reported it as lost or destroyed,’ I said, wryly.

The door opened. It was Mike Rogers and Sue was with him. Carefully, making sure that my hand was hidden by my body, I slipped the bug back into my jacket pocket and pulled myself together.

‘Did we miss something?’ Mike asked.

I didn’t answer. Peter turned away and, with Mike’s help, continued his work. I was going to have to make a couple of calls to see what I could find out about the listening device. The first would be to an old friend, Toni Fellowes.

‘You did a great job,’ said Sue, extending her hand to me.

Mike raised an eyebrow and winked at me. I offered my thanks and headed for the control room. It was time to see about arranging a lift home and to give some thought as to how I might be able to help Doug Powell.