At first, Mallory couldn’t understand what she meant, but gradually the realisation crept over him. The lines of blue force that had crisscrossed the hill also ran through this place, though at that point they were invisible. But Mallory could feel them even through the soles of his boots, buzzing gently, soothing him with their caress. He stepped forward, following the faint sensation. It led directly to the right-hand path.

‘So we’ve got to trust that the freaky Blue Fire is leading us to the right one,’ he said.

‘That’s the point, isn’t it? We’re showing trust — and humility. Two qualities that mean we’re worthy to find what lies ahead.’

‘I’m glad one of us has got it all figured out.’

As he prepared to take the first step on the path, Sophie took his hand and squeezed. ‘It’s the Pendragon Spirit, Mallory. Think of what it represents.’

Her words reassured him and, tentatively, he edged out on to the precarious path. It felt like tightrope walking; he had to hold his arms out to keep his balance, not looking down, moving one foot in front of the other only when he was sure he was secure and balanced. Sophie followed in his footsteps.

When they’d gone about twenty feet, Mallory realised that the other two paths had disappeared. Theirs was the only path leading into the gloom ahead.

Mallory was soon sleeked with sweat, his concentration so intense that his head hurt. He didn’t say a word to Sophie for fear of distracting her, but every time he heard her foot skid slightly on the stone, his heart beat wildly.

He didn’t know how they carried on. Each step became a mountain to climb, each movement a mantra of whispered prayer. But finally they reached solid ground and collapsed on to the stone flags, hugging each other in relief.

When they had recovered, they found themselves confronted by two stone doors. An image of a dragon eating its own tail was carved in the stone lintel over the point where the doors met.