‘Did the chairman die of a heart attack?’ asked the judge, cutting to the quick.

‘He may well have done,’ said William. ‘But I’m more interested in what caused that heart attack.’

Once again, all three of them waited impatiently while William placed a little mustard on the side of his plate.

‘Are you going to tell us the answer,’ Beth finally demanded, ‘or do we have to wait until our food’s gone cold?’

William put down his knife, wiped his mouth with a napkin, and said, ‘I’m able to tell you how the murder was committed, as long as you don’t breathe a word to anyone.’

‘And that includes you, my dear,’ said George, smiling at his wife.

William waited until Franco had refilled their wine glasses before producing James’s seating plan and placing it in the centre of the table.

He allowed them a few moments to study it, before he continued. ‘First, note that Hamish Buchanan is seated on the left-hand side of the table, between his mother and Flora Buchanan on his left.’

‘Who’s she?’ asked Catherine.

‘Fraser Buchanan’s sister. The formidable grande dame of the company, who the rest of the family are in awe of.’

‘And next to her?’ enquired the judge, peering down at the plan.

‘Dr Lockhart, whose sole purpose in life was to keep the chairman alive. But not on this occasion.’

This revelation silenced the three of them for a moment, giving William the chance to enjoy a forkful of steak.

‘And on his left?’ asked Beth.

‘Alice Buchanan, James’s mother and the wife of Angus Buchanan’ – he moved his finger across to the other side of the table – ‘who recently replaced his brother Hamish as deputy chairman of the company.’

‘I have a feeling that side of the table isn’t going to be important,’ said the judge.

‘A shrewd observation,’ said William, ‘but you’ll still have to concentrate if you’re to work out what Hamish Buchanan was up to. Everyone saw him take a drink from his hip flask during dinner, which caused his father to pointedly ask what he was drinking, as he suspected it was whisky or brandy, despite Hamish having just assured him he was on the wagon.’

No one interrupted as William put down his knife and fork.

‘Hamish claimed the flask only contained a mild sedative that had been given to him by Dr Lockhart to help him sleep. But the chairman demanded it was passed to him so he could check for himself. Their first mistake.’ William paused to allow Franco to refill their wine glasses.

‘Where was I?’ he said once Franco had put the wine back in the ice bucket.

‘Hamish was passing his hip flask to his father, who was seated at the top of the table,’ Beth reminded him.

‘Ah yes,’ said William. ‘So, Hamish handed the flask to Great-Aunt Flora, who passed it on to the doctor, who in turn gave it to Alice, who finally handed it to the chairman.’ He took a sip of wine while they continued to study the table plan. ‘The chairman swallowed a long draught from the flask,’ he continued, ‘and although he found it tasted unpleasant, it clearly wasn’t alcohol, and therefore he assumed it must be the medicine Dr Lockhart had prescribed. He then passed the hip flask back to his son at the other end of the table.’