Twenty minutes later I drove up the steep hill behind Molloy’s car. Derek’s orange cycling jersey was just ahead, disappearing and reappearing as he rounded one of the hairpin bends. A minute later and he was visible again, pushing with huge determination up an almost impossible gradient. He must have heard us behind him – Molloy was beeping at him to pull in – but still he kept going. There was no way he could outrun two cars, but he wasn’t going to stop until he absolutely had to. It was impossible not to admire the man’s grit.

On a short straight stretch, Molloy overtook him and parked crossways across the road, cutting him off. Finally, Derek came to a stop and he stood, one leg on either side of the bike.

I pulled in behind and he smiled when he saw me, sweat dripping down his face. “I was right. It is a great place for a cycle.”

“Mr Jameson,” Molloy started.

“Sergeant.” Derek nodded in acknowledgement; hands taut on the handlebars.

“May I have a word with you?”

“Of course.” Derek dropped the bike, placing it carefully onto the grass verge. Then he straightened and positioned himself in that strange stance I’d witnessed the first day outside Phyllis’s bookshop. I now knew the reason behind it.

“I rang Phyllis as you suggested,” he said to me. “Poor Mary, loyal to the end. My brother wouldn’t appreciate that, of course. Bob would have left her without a backward glance.”

“You knew he was leaving?” Molloy asked.

“Not where, he wouldn’t tell me that. Somewhere that doesn’t have an extradition agreement with Ireland would be my guess,” Derek said with a smile. He winced suddenly as if he was in pain and he sat down onto the closest rock using his hand to steady himself as he lowered himself down. “Look, I’ll make things easy for you. As I’m sure you’ve guessed, I killed my brother.”

And there it was.

“Why?” Molloy asked.

“You know, I’ve been thinking about that since it happened, and I think I’ve been meaning to do it for years. Possibly since we came out of the womb.” He gave another half-smile. “Him first, of course. Our mother said I was half-starved in there because Bob took everything. Sign of things to come.”

Molloy crossed his arms impatiently, but Derek wasn’t going to be rushed.

“Freud would say it’s self-loathing since twins are a mirror of each other. But I’d rather not think that, if you don’t mind.” He paused. “Plus, though I may have wanted to kill him, I didn’t actually intend to. Bob’s death was an unintended consequence of my actions.”

“What happened, Mr Jameson?” Molloy had had enough of Derek’s philosophising.