‘As I say, it’s not my field,’ Rose replied. ‘Like most people, I’d be inclined to dismiss it all as complete hocus pocus.’ He smiled. ‘Though it has to be said that few esoteric cults have endured so well over the centuries. All the way from ancient Egypt and China, right through the Dark Ages and medieval times and onwards into the Renaissance-it’s a sub-current that keeps resurfacing all throughout history.’ The professor stretched back in the worn leather chair as he spoke, adopting the tutor pose that was second nature to him. ‘Though heaven knows what they were up to, or thought they were up to-turning lead into gold, creating magical potions, elixirs of life, and all the rest of it.’

‘I take it you don’t believe in the possibility of an alchemical elixir that could cure the sick?’

Rose frowned, noticing Ben’s deadpan expression and wondering where he was going with this. ‘I think that if they’d developed a magic remedy for plague, pox, cholera, typhus, and all the other diseases that have ravaged us through history, we’d have known about it.’ He shrugged. ‘The problem is it’s all so speculative. Nobody really knows what the alchemists might have discovered. Alchemy’s famous for its inscrutability-all that cloak-and-dagger stuff, secret brotherhoods, riddles and codes and supposed hidden knowledge. Personally I don’t think there was much substance to any of it.’

‘Why all the obscurity?’ Ben asked, thinking of the reading he’d been doing over the last couple of days, running Internet searches on terms like ‘ancient know ledge’ and ‘secrets of alchemy’ and wading through one esoteric website after another. He’d turned up a wide variety of alchemical writings, ranging from the present day back to the fourteenth century. They all shared the same baffling and grandiose language, the same dark air of secrecy. He hadn’t been able to decide how much of it was genuine and how much was just esoteric posturing for the benefit of the credulous devotees they’d been attracting over the centuries.

‘If I wanted to be cynical I’d say it was because they didn’t actually have anything worth revealing,’ Rose grinned. ‘But you’ve also got to remember that alchemists had powerful enemies, and perhaps some of their obsession with secrecy was a way of protecting themselves.’

‘Against what?’

‘Well, at one end of the scale there were the sharks and speculators who preyed on them,’ Rose said. ‘Once in a while some hapless alchemist who’d bragged too loudly about gold-making would be kidnapped and made to tell how it was done. When they failed to come up with the goods, which of course they probably always did, they’d end up hanging from a tree.’ The professor paused. ‘But their real enemy was the Church, especially in Europe, where they were forever burning them as heretics and witches. Look what the Catholic Inquisition did to the Cathars in medieval France, on the direct orders of Pope Innocent III. They called the liquidation of an entire people God’s work. Nowadays we call it genocide.’

‘I’ve heard of the Cathars,’ Ben said. ‘Can you tell me more?’

Rose took off his glasses and polished them with the end of his tie. ‘It’s a terrible story,’ he said. ‘They were a fairly widespread medieval religious movement that mainly occupied the part of southern France now known as the Languedoc. They took their name from the Greek word Catharos, meaning “pure”. Their religious beliefs were a little radical in that they regarded God as a kind of cosmic principle of love. They didn’t attribute much importance to Christ, and may not even have believed he existed. Their idea was that, even if he had existed, he certainly couldn’t have been the son of God. They believed that all matter was fundamentally crude and corrupt, including human beings. For them, religious worship was all about spiritualizing, perfecting and transforming that base matter to attain union with the Divine.’

Ben smiled. ‘I can see how those views might have upset the orthodoxy a little.’

‘Absolutely,’ Rose said. ‘The Cathars had essentially created a free state that the Church couldn’t control. Worse, they were openly preaching ideas that could seriously undermine its credibility and authority.’

‘Were the Cathars alchemists?’ Ben asked. ‘The part about transforming base matter sounds very like the ideas of alchemy.’

‘I don’t think anyone knows that for certain,’ Rose said. ‘As a historian, I wouldn’t stick my neck out on that one. But you’re quite right. The alchemical concept of purifying base matter into something more perfect and incorruptible is certainly well in tune with Cathar beliefs. We’ll never know for sure, because the Cathars never lived long enough to tell the tale.’

‘What happened to them?’

‘In a nutshell, mass extermination,’ Rose said. ‘When Pope Innocent III came to power in 1198, the alleged heresies of the Cathars gave him a magnificent excuse to extend and reinforce the Church’s powers. Ten years later he put together a formidable army of knights, the biggest ever seen in Europe at that time. These were hardened soldiers, many of who had seen service fighting in the Holy Land. Under the command of former crusader Simon de Monfort, who was also the Duke of Leicester, this huge military force invaded the Languedoc and one by one they massacred every fortress, town and village with even the remotest Cathar connection. De Monfort became known as the “glaive de l’eglise”.’

‘The sword of the Church,’ Ben translated.

Rose nodded. ‘And he meant business. Reports at the time spoke of a hundred thousand men, women and children slaughtered at Béziers alone. Over the next few years the Pope’s army swept over the entire region, destroying everything in its path and burning alive anyone who didn’t die under the sword. At Lavaur in 1211 they threw four hundred Cathar heretics on the pyre.’

‘Nice,’ Ben said.

‘It was a vile affair,’ Rose continued. ‘And it was during this time that the Catholic Church formed its Inquisition, a new wing of Church officialdom to lend greater authority to the atrocities performed by the army. They oversaw duties of interrogation, torture and execution. They were answerable only to the Pope personally. Their power was absolute. At one point in 1242, the Inquisitors were acting so bloodthirstily that a detachment of disgusted knights broke away from their station and slaughtered a whole bunch of them at a place called Avignonet. Of course, the rebel knights were quickly suppressed. Then, finally in 1243, after the Cathar resistance had held out much longer than anyone had anticipated, the Pope decided it was time to finish them off once and for all. Eight thousand knights laid siege to the last Cathar stronghold, the mountaintop castle of Montségur, firing enormous rocks at its ramparts from their catapults for ten solid months until the Cathars were finally betrayed and forced to surrender. Two hundred of the poor souls were brought down the mountain and roasted alive by the Inquisitors. And that was more or less the end of them. The end of one of the most scandalous holocausts of all time.’

‘I can see alchemical heresy might have been a risky thing to get into,’ Ben said.

‘Still is, in some ways,’ Rose replied playfully.

Ben was taken aback. ‘What?’

The professor threw his head back and laughed. ‘I don’t mean they’re still executing heretics in the public square. I was thinking of the danger for people like myself, academics or scientists. The reason nobody wants to touch this subject with a bargepole is the reputation you’d get for being a crank. Every so often someone takes a bite of the forbidden apple and their head rolls. Some poor sod got the sack for just that reason, a while ago.’

‘What happened?’

‘It was at a Parisian university. American biology lecturer got into hot water over some unauthorized research…’