‘Being involved in it has been a revelation to me, Mr Skillen. However, let me pass on my news. I met an old friend of a mine at the club. Stephen Quine was our regimental doctor and an excellent one at that. Don’t worry,’ he went on, ‘I’m not going to bore you with military memoirs. Dr Quine now makes a living dissecting the bodies of murder victims.’

‘Was he involved in Sir Roger’s post-mortem?’ asked Peter.

‘Indeed, he was. More recently, he dealt with the case of a man who was shot dead in St James’s Park and, almost as soon as that had been done, he was summoned to look at a murder victim being examined by a colleague.’

‘I don’t quite see what relevance this has,’ said Peter.

‘Bear with me and you will. The second case I mentioned refers to a man shot dead later today in a house in Marylebone.’

‘So?’

‘Including Sir Roger, we have three men shot through the skull.’

‘Go on.’

‘Dr Quine believes that, in each case, the same pistol was involved.’

‘That’s a very big assumption to make,’ said Peter, sceptically.

‘Surgeons never make assumptions, Mr Skillen,’ said Golightly. ‘They deal in hard facts. I find the evidence compelling. The bullet that was taken from Sir Roger’s brain was of an unusual shape and so was the one taken from the victim in St James’s Park. Since they were identical, the bullets must almost certainly have come from the same mould. But there’s another clinching detail.’

‘What is it?’ asked Paul.

‘Each bullet had a letter “D” scratched into it.’

‘Was that the initial letter of the killer’s name?’

‘I’ve no idea,’ said Golightly, ‘but let’s move on to the third victim. Dr Quine had mentioned what he’d found to a colleague so you can understand why the man called him in. What he’d extracted from the brain of the third victim was a bullet of the same unusual shape and bearing the same signature. That’s irrefutable evidence in my mind that the assassin who took Sir Roger’s life went on to murder two more victims. I thought you’d find that interesting.’

‘It’s fascinating,’ said Peter.

‘And it raises the question of who those victims are,’ said Paul. ‘My guess is that they might be people involved in the plot. The assassin was ruthless. He works on the principle that the best way to ensure his own safety is to eliminate the only people aware of his guilt.’

‘Wait a moment, Paul. You’re forgetting Orsino Price. He was also an accomplice, yet he wasn’t shot through the skull. Someone stabbed him to death in an alleyway.’

‘In that instance, a dagger was as quick as a bullet and far less likely to attract attention. Hired killers are usually adept with a range of weapons.’