‘Thank you,’ said Beth, not sure if Christina was lying, or genuinely didn’t know where he was. William would have to make that decision.

Christina turned to leave the room, looking a little more confident than when she’d entered it.

Once she’d closed the door behind her, Beth picked up the phone on her desk, but hesitated for a moment before doing something she knew William normally wouldn’t approve of. She dialled his private number at the Yard.

• • •

‘You’re being paid a thousand pounds a week to sleep with me?’ said Ross in disbelief.

‘Plus the rent on this apartment and a clothes allowance.’

‘By who?’

‘By whom.’

‘By whom?’

‘The escort agency in Paris that employed me to seduce you.’

‘And what do they expect in return?’

‘I have to report back everything you tell me, however inconsequential or irrelevant it might seem to me.’

‘And have you?’

‘Yes, but unfortunately you never talk about your work, so I can’t be sure how much longer they’ll keep me on.’

Ross remained silent for some time, before he finally said, ‘Then we’ll have to do something about that. You can now tell them that at last you’ve made a breakthrough.’

‘But you’d never be disloyal to the man you call The Hawk.’

‘You’re right, but that doesn’t stop me supplying you with lots of irrelevant information,’ he said, clearly now enjoying himself. ‘I’d have to brief the commander, of course, and he’s bound to ask me who’s paying the escort agency.’

‘I’ve no idea,’ said Jo, without guile.

‘I’m pretty sure I know who it is,’ said Ross. ‘Have you ever come across a Miles Faulkner or Captain Ralph Neville?’

‘No. All I can tell you is that I was introduced to a man who briefed me about you and told me I should report once a week to a Mr Booth Watson.’

‘That clinches it,’ said Ross, taking her in his arms. ‘But there’s one more thing I still need to know before you earn your next thousand pounds.’

‘Yes?’

‘Will you marry me?’

• • •

‘So what did The Hawk have to say about my little exchange with Christina?’

‘He couldn’t have been more grateful for your “special constable” contribution. All we can do now is hope that she’ll pass on your “highly confidential” slip of the tongue to Booth Watson. If she does, I have a feeling Faulkner won’t be able to resist making a trip to Scotland so he can view the Caravaggio for himself.’

‘That would also prove which side Christina’s really on,’ said Beth.

‘I’m not sure even she knows which side she’s really on.’

‘But if she loans the gallery the Frans Hals …’

‘If Faulkner goes along with that, you should try to convince Christina that you now trust her, and believe every word she says.’

‘Even she doesn’t believe every word she says,’ replied Beth.

‘You’re learning quickly,’ said William, ‘and I’m fairly sure she’ll tell Booth Watson about the Caravaggio. It will convince them she’s still on their side.’