‘You spent a long time at the theatre.’

‘Not really. No more than forty minutes. I’m sure the stage-door manager will have seen me leave.’

‘You signed in and out?’

Longhurst thought back. ‘No. I don’t think I did. The pen was out of ink. But you can ask … I made no attempt not to be seen.’

‘Thank you, Mr Longhurst. You’ve been very open with us. I’m sorry we had to make you go through it all again.’

It was rare to hear Hawthorne apologise for anything and the moment we were back in the street, I had to ask: ‘Did you believe him?’

We were walking along Queen Square, a private garden laid out on one side. The sun was still shining and the trees were in blossom, not that the sight of them did much for me. Hawthorne was already deep in thought. ‘Believe what, exactly?’ he said.

Why did he have to be so difficult?

‘All along, we’ve assumed the dagger was taken after the party, at night,’ I explained. ‘But Martin Longhurst could have taken it early the following morning.’

‘I haven’t assumed anything,’ Hawthorne said.

I ignored this. ‘An hour and a half would have been enough time to go to Little Venice and back again. He could have killed Harriet Throsby and gone straight into work.’

‘Covered in blood?’

‘He could have worn a coat!’

‘But why would he have wanted to frame you?’ he asked.

‘Well, you heard what he said. His client’s going bankrupt. Maybe he blamed me for the play.’

Hawthorne stopped. ‘It’s just possible that Longhurst could have picked up the dagger when he went to the theatre the next morning,’ he said. ‘But there are three questions you’ve got to ask yourself. How did he know it was there, and if he happened to come across it, how would he know it was yours?’

‘And the third question?’

‘How did he get hold of a strand of your hair?’

It was true. ‘Longhurst wasn’t anywhere near me,’ I admitted. ‘He couldn’t have got a sample of my hair … not unless he followed me into a hairdresser, and I haven’t been to one for weeks!’

Hawthorne stopped. I could see the main road and Holborn station ahead of us.

‘Let’s just suppose for a minute that the two things – the murder and your involvement – aren’t connected,’ he said. ‘Let’s imagine that you’re completely irrelevant.’

‘Thanks!’

‘An old man died in the village of Moxham Heath. Two kids killed him. And Harriet turned it all into a book.’

‘You think someone didn’t like what she wrote?’

‘Nobody ever liked what she wrote. That was her intention. But emotions always run high when someone dies. And you’ve got to ask yourself – what was that book doing, sitting on Harriet’s desk?’

‘Bad Boys …’

‘Maybe she was trying to tell us something.’

‘We’re not going to Moxham Heath, are we?’

‘Tony, mate. Cara Grunshaw can’t be too far behind. By the end of today, she’s going to have everything she needs to nail you.’