So I was happy to find myself there on a bright June morning, three months before my new novel, The Word Is Murder, was due to be published. I’d been asked to come in by my editor, Graham Lucas, who’d surprised me with a telephone call.

‘Are you busy?’ he had asked. ‘We’d like to talk about publicity.’ As always, he went straight to the point.

Advance proofs of the book had already gone out and apparently they had been well received – not that I’d have heard otherwise. Publishers are brilliant at keeping bad news from authors.

‘What time?’ I asked.

‘Could you manage Tuesday? Eleven o’clock?’ There was a pause and then: ‘We also want to meet Hawthorne.’

‘Oh.’ I should have expected it, but even so I was surprised. ‘Why?’

‘We think he could make a serious difference to the sales. After all, he is the co-author.’

‘No, he’s not. He didn’t write any of it!’

‘It’s his story. We see you as a team.’

‘Actually, we’re not that close.’

‘I think the public will be very interested in him. I mean . . . in the two of you together. Will you talk to him?’

‘Well, I can ask him.’

‘Eleven o’clock.’ Graham hung up.

I was more than a little deflated as I put the phone down. It was true that the book had been Hawthorne’s idea. He was an ex-detective who worked as a consultant to the police, helping them with their more complicated investigations. He’d first approached me to write about him while he was looking into the murder of a wealthy widow in west London, but I’d been reluctant from the start, mainly because I preferred to make up my own stories. Certainly, I had never thought of the book as a collaboration and I wasn’t sure I liked the idea of sharing the stage – any stage – with him.

But the more I thought about it, the more I realised that this could play to my advantage. I had now followed Hawthorne on two investigations – and ‘follow’ is the right word. Although I was meant to be his biographer, he never actually explained anything of what he was doing and seemed to enjoy keeping me several steps behind him, always in the dark. I had missed every clue that had led him to Diana Cowper’s killer and because of my own stupidity I had almost got killed myself. I had made even more catastrophic errors on our next case, the murder of a divorce lawyer in Hampstead, and I wasn’t entirely sure I could write the second book without making myself look ridiculous.