I feel her pain – the border between England and Wales is blessed with amazing views (if you like hills and sheep) but isn’t exactly known for its entertainment options, and the poor thing must have heard my talk a dozen times. Her mum tries to hug her, but the girl shoves her off and takes out her phone. The casual indifference of the gesture cuts a hole in my chest and jealousy reaches in and squeezes my heart, quickly followed by resentment. Between them, they have a mighty strong grip.

Get it together, Ivy. Focus on work.

I avert my eyes, uncomfortable with my own feelings, and bring my attention to the dozen people who’ve gathered to hear my talk. The man in the anorak stares at me, his facial muscles rigid as if they’ve been frozen into place. I wait for him to say something, or at least blink, but he doesn’t. We get some odd characters at the centre; dealing with them is part of the job. Even so, I can’t help feeling a little unnerved. He strokes his beard, repeating the movement robotically, and I wonder if he has a nervous tic or anxiety. I smile reassuringly at him, then thank the group for their patience and scan the walkways for latecomers.

A family enters through the hanging plastic strips that cover the entrance and something occurs to me. I included both my work and home addresses in the letter, so my mum might turn up here.

No. It’s so far to come; surely she’d ring me first. I don’t care how hard it is to get to Bardsey. If she doesn’t call by the end of the day, I’ll phone in sick and go to the island tomorrow. I have to know if it’s her.

A loud gasp brings me back to reality. People are pointing and staring at a spot above my head.

‘What the hell are they?’ asks jumpsuit woman. I glance up and fluttering over me are three huge grey moths – acherontia atropos, to be precise. These ones are adults of the species, each with a twelve-centimetre wingspan.

‘They’re death’s head hawkmoths,’ I tell my audience. ‘They get their name from the skull-shaped pattern that adorns their thorax.’

The sight of them makes me shiver, despite the heat. Not because they’re an omen of death, but because there’s something unnatural about the way they circle over me. Butterflies and moths usually fly haphazardly, going one way and then another, not around and around in a neat pattern. But this is like watching a few frames of film on repeat.

A high-pitched, pulsating screech fills the air and I raise my voice. ‘They make that noise to scare away predators. It’s particular to the species; not many moths do that.’

A few people in the crowd nod and look relieved, and then the creatures flit towards a fern and the sound disappears as quickly as it started. Unable to pull my gaze away, I watch their strange flight with a growing sense of unease. I’ve never seen anything here fly like that.