"The only thing I know about Wimbledon is the tennis." Derwent drummed his fingers on the steering wheel.

I stared at the map. "What do you need to know? It's an expensive place to live. Smart. Out of your price range. Not the sort of place we usually fetch up. Still two miles away at a rough estimate, and God knows how long that's going to take."

"Lights are changing, Kerrigan. I'm going to go on straight."

"No, don't do that." Straight ahead of us was a queue of cars that stretched to infinity, or at least the A3. I turned the map around, desperately searching for the right road. "Left. Turn left."

"I'm in the wrong lane." The car surged forward, going straight into the one-way system from hell. "Should have decided sooner."

"I don't know why you sound so smug. We're both going to be stuck in the same traffic."

"Yeah, but it's your fault. So I can enjoy myself by blaming you."

"It's not my fault that you broke your satnav." The ice in my voice did nothing to cool the temperature in the car; I could feel sweat trickling down my back and shifted in my seat. The windows were down but the air was stagnant, hot even though the sun had set hours earlier. August in London, and the weather was at its worst. "Since we're stationary, do you mind putting the air conditioning on?"

"Waste of petrol. Someone's got to think of the environment." He stuck his head out of his window and sniffed enthusiastically. "Fresh air is better for you."

A hundred exhausts belched fumes in front of us. "This air is not fresh."

"Nor are my socks," Derwent admitted, sticking a finger down the side of his shoe and proving his point with a waft of sweaty-foot smell. My nose wrinkled and I turned my face away, not caring that he found it funny.

"Why is there so much traffic at this time of night anyway?"

"Need you ask? Roadworks. It goes down to one lane from three. We should never have come this way." Derwent inched forward although the car in front hadn't moved. "Almost midnight. What were you planning to do this evening?"

I had hoped for an early night, but I knew better than to say anything that hinted at bed. The DI was as quick to go after innuendo as a terrier barreling down a rat hole. "Nothing much. You?"

"Nothing you want to hear about, I imagine." A sidelong glance. "Your loss."

"I doubt that." I knew very little of his private life, but that was precisely as much as I wanted to know about it. I just wished he felt the same way about me.

"What about your boyfriend?"

"What about him?"

"Is he at home?"

"He's working." And that's all I'm saying, so move on.

"You're probably pleased to have something to do. Gets you out of the house, doesn't it?"

Thank God. Work talk. "It sounds like an interesting case."

"It sounds like a domestic." Derwent rubbed a hand over the back of his neck and looked at it, then wiped it down his trouser leg. "I'm sweating like a pedo in a playground."

He was reliably, casually offensive, but every now and then he still managed to shock me. I had decided that he was an acquired taste, and that I could get to like him some day. Today was not that day.

"Look, if you don't take the next left we're going to be here until midnight."

"It's one-way." He was leaning forward to see, hugging the steering wheel. I peered in the same direction, seeing the no-entry signs.

"Oh, bollocks."

"I could blue light it."

"Not a good idea," I said automatically. There were strict rules governing when we could travel on blues and twos. Getting to work was not an emergency.

Derwent looked at me sideways. His hair was ruffled and he'd caught the sun across the bridge of his nose. He looked all of eight years old. "Please?"

"Why are you asking me? You're the senior officer."

"That's right. I am." He sounded pleased at the reminder. "Well, off we go. Hit it, Kerrigan."

The siren hadn't finished its first whoop before Derwent had pulled out of our line of traffic, making for our illegal turn. We had two wheels on the pavement most of the way. I closed my eyes and muttered, more or less involuntarily, "Jesus, Mary and Joseph."

"Talk holy to me, Kerrigan. You know I love it when you pray."

"Just concentrate on what you're doing, okay?" The streets weren't empty enough for rally driving. Because of the weather, people were still out walking their dogs or jogging, in spite of how late it was. They really weren't expecting to be confronted with an unmarked car bearing down on them from the wrong direction, even if we did have our blue lights flashing.

We were, however, making progress, and as Derwent pulled out onto the main road — causing a bus to slam on its brakes — he gave me a wide grin. "That's better, isn't it?"

"Better than sitting in a traffic jam," I allowed.

He shook his head. "You just can't say it, can you? 'I was wrong. You were right, Josh. I should always listen to you.'"

"You're right. I can't say that. Turn right after these traffic lights."

"Up the hill," Derwent checked.

"That's where we're going."

Up the hill. Up into the rarefied air of Wimbledon Village, the pretty, exclusive little enclave where expensive boutiques, delis, galleries and cafés catered to the tastes of the locals and their apparent desire to spend my annual salary on fripperies and cappuccinos. Up to where the houses were detached, set back from the road, and priced in multiple millions. It was leafy and lavish and a different world from where I lived, even though that was only a few miles away as the crow flew.

Derwent was paying scant attention to the road, leaning into my personal space. He whistled. "Look at that one."

"The house?" It was a white-painted mansion with yew lollipops on either side of the front door.

"The Aston Martin, Kerrigan. I couldn't give a fuck about the house."

"Think that's a footballer's gaff?"

"Could be. Someone with a few hundred grand to spend on one of their cars. I saw it on Top Gear. Beautiful, isn't it?" He had slowed to a crawl and was creeping along, hugging the curb as he stared at the car. A BMW overtook us with a blast from its horn and Derwent raised a hand to acknowledge it, hopelessly distracted.

"They'll call the police if you're not careful. Stop drooling."

"That car or a night with Angelina Jolie. I'm not even joking, I wouldn't stop to think about it."

"I wouldn't worry. You're not likely to have to choose any time soon."

"Angelina would understand," he said with conviction. "She'd appreciate it. She'd feel the same way." He flicked a look at me. "You don't get it, do you? It's just a car to you."

"It's a means of getting from A to B. It may not be quite as beautiful, but so is the one that we're sitting in currently. And I would like to get to B before the SOCOs and the boss have packed up and headed home."

"Ooh, the boss. Why didn't you say? We'd better hurry." Derwent took off with a wheel spin that left six feet of rubber on the road.

I ignored the sarcasm and the stunt driving and said nothing else except to direct him through the narrow tree-lined roads until we reached the white wooden barrier that cut off Endsleigh Drive from its neighbors.

"Cul-de-sac with no vehicular access except for residents. So whoever did it had to walk there."

"Unless it was one of the residents."

Derwent frowned. "Bit extreme for a neighborly dispute." He...