Counting my breaths so I timed it perfectly, I let my foot slip again. This time, however, I cried out sharply and fell against William. My right hand grabbed his wrist, ostensibly to stop me crashing into him and making us all topple like a line of dominoes.

William grunted back and tried to pull away but I looked at him desperately. With more scree sliding around our feet, he also lost his balance and was forced to grab me. By this point, I’d loosened the watch enough for my purposes. Expensive ones like these, with leather buckles, were always the easiest. Keeping my finger in the right spot to avoid the prong from slipping back in, the buckle detached completely and I palmed the watch.

‘I’m so sorry,’ I said again.

‘Aifric said to be more careful!’ Kincaid snapped.

I hung my head apologetically. As soon as he’d righted himself and was following the others down, I passed the watch back to Bob.

‘Uh Integrity,’ he whispered in my ear. ‘You are a goddess.’

I smiled and took out the letter opener, gesturing to it and hoping he’d do as I asked.

‘Very well,’ he said. ‘But only so I can examine this beauty in more detail.’

I shook my head and pointed ahead. I needed him to wait until the next key was used. A flash of light here would be impossible to hide.

Sensing rather than seeing him nod, I flicked my hair out to cover both the watch and him. There was a sliver of light ahead. At least we were almost at the next lock.

‘We’ve made it to the cavern,’ I heard Dorienne Darroch say.

‘Thank fuck,’ Kincaid muttered.

One by one we squeezed out. The relief of getting back to a more open space was overwhelming. I gulped in air and looked around. The light was deceptive. Rather than natural light filtering in from above, it was an eerie glow reflecting from thousands of green lights in the roof of the cavern to the dark pools below.

‘Glow worms,’ Bob hissed in my ear. ‘Nasty unfriendly creatures.’

Diana gasped. ‘Is it magic?’

‘Glow worms,’ I said knowledgeably. ‘Lovely little things.’

She sent me an approving glance. Perhaps Bob was right and she was feeling less antagonistic. The genie, however, was unimpressed at my showing off and flicked my ear lobe. I jumped half a foot in the air.

‘I’m still a bit stiff from all that horse riding,’ I explained when the others looked at me, puzzled.

‘You or me, boy?’ Aifric said, addressing Byron.

Byron gestured ahead. ‘Please.’

Aifric gave a tiny smile and stepped up. Just as before, we stood back to give him privacy. I put my hand on the letter opener to remind Bob to make tracks – but this time he timed it rather badly. The flash of light came about three seconds after Aifric whispered his true name.