‘Four and a third minutes,’ he panted. ‘And the cast made it in three. It’s impossible.’

‘You don’t seem as disappointed as I’d have expected,’ said Fox.

‘Don’t I? I – I’m not sure. I may be going dotty. I am going dotty. Let’s check the possibles, Fox. Which is Number One?’

‘Macduff? He killed Macbeth as we were meant to think. Duel. Chased him off. Killed him. Fixed the head on the weapon and came on with Seyton carrying it behind him. Sounds simple.’

‘But isn’t. What was Macbeth doing? Macduff chased him in and then had to dodge about, take the dummy head off the claidheamh-mor, raise it and do the fell deed.’

‘Yerse.’

‘Did Macbeth lie there and allow him to get on with it? And how about the time? If I couldn’t do it in three minutes, nobody else could.’

‘Well, no. No.’

‘Next?’

‘Banquo?’ Fox suggested.

‘He could have done it. He was hanging about in that region after he was called. He could have slipped in and removed the dummy head. Waited there for the end of the duel. Done it. Fixed the head. And walked out in plenty of time for the second curtain call. He was wearing his bloodied cloak, which would have accounted for any awkward stains. Next?’

‘Duncan and/or one of his sons. Well,’ said Fox apologetically, ‘it’s silly, I know, but they could have. If nobody was watching them. And they could have come out just when nobody was there. If it wasn’t so beastly it would be funny. The old boy rolling up his sleeves and settling his crown and wading in. And, by the way, if there were two of them the time thing vanishes. The King beheads him and drags the body over and puts the dummy head by it while his son puts the real head on the weapon and places them in the corner. However,’ said Mr Fox, ‘it is silly. How about one of the witches? The man-witch?’

‘Rangi? Partly Maori. He was wonderful. Those grimaces and the dance. He was possessed. He was also with his girls, and you noted it, all through the crucial time.’

‘All right then. The other obvious one. Gaston,’ said Fox moodily.

‘But why obvious? Well, because he’s a bit dotty – but that’s not enough. Or is it? And again: time. We’ve got to face it, Fox. For all of them. Except for the royal family, Banquo, and the witches – time! Rangi could have taken a girl in to fix the head on the claidheamh-mor and thus saved about a minute. It’s impossible to imagine anybody collaborating with the exuberant Gaston.’

‘Anyway,’ said Fox, ‘we’ve got to face it. They were all too busy fighting and on-going.’

‘It’s all approximate. Counsel for the defence, whatever the defence might be, would make mincemeat of it.’