But none of them seemed like an option on that hot summer night, as Kate spoke those words, and we stood facing each other around Ambrose’s body.

‘Thea?’ Kate asked, and she nodded, uncertainly, and put her hands to her head.

‘It – it seems like it’s the only way.’

‘It can’t be,’ Fatima said, but she didn’t say it as if she believed it, she said it like someone trying to come to terms with something they know to be true, but can’t bear to accept. ‘It can’t be. There must be another way. Isn’t there something we could do? Raise some money?’

‘It’s not just the money though, is it?’ Thea said. She ran her hands through her hair. ‘Kate’s fifteen. They won’t let her live alone.’

‘But this is mad,’ Fatima said, and there was despair in her voice as she looked around the circle. ‘Please, Kate, please let me call the police.’

‘No,’ Kate said harshly. She turned to face Fatima, and there was a strange mix of pleading desperation, and reluctance in her face. ‘Look, I’m not asking you to help me if you feel you can’t, but please, please don’t tell the police. I’ll do it, I swear. I’ll report him missing. But not now.’

‘But he’s dead!’ Fatima sobbed out, and as she said the words something in Kate seemed to snap and she grabbed Fatima by the wrist, almost as if she was about to strike her.

‘Do you think I don’t know that?’ she cried, and the despair in her voice and face – I hope I never witness another human being go through that again. ‘That’s why this is the only – the only –’

For a moment I thought she might be about to lose control completely – and in a way it would have been a relief, to watch her scream and rail against what had happened, and the great hammer blow that had been struck against the security of her existence.

But whatever storm was passing through her, she reined it in with a great effort, and her face, when she let Fatima’s wrist drop, was calm.

‘Will you help me?’ she said.

And one by one, first Fatima, then Thea, and then last of all me, we nodded.

We were respectful, or as respectful as we could be. We wrapped the body in a groundsheet and carried it as far as we could, to a place where Ambrose had loved to sketch, a little headland a few hundred yards down the Reach, towards the sea, where the views were at their most beautiful, where the track petered out and no cars could drive, and where few people came, except the odd dog walker and the fishermen with their boats and lines.

There, among the reeds, we dug a hole, taking it in turns with the shovel until our arms ached and our backs screamed, and we tipped Ambrose in.

That was the worst part. No dignified lowering – we couldn’t. He was too heavy, even with four of us, and the hole was too deep and too narrow. The sound he made as he hit the wet, shaley bottom – it was like a kind of smack. I hear it still, sometimes, in my dreams.

He lay face down, completely still, and behind me I heard Kate give a kind of retching, choking sob, and she fell to her knees in the sand, burying her face in her hands.

‘Cover him up,’ Thea said, her voice hard. ‘Give me the shovel.’

Slap. The sound of wet sand flung into a makeshift grave. Slap. Slap.

And over it all, the shushing of the waves on the shore, and Kate’s dry terrible sobs, reminding us what we were doing.

At last the hole was full and the tide rose to cover the marks we’d made, smoothing over our muddied, troubled footprints, and the scar we had cut in the bank. And we stumbled back with the torn groundsheet in our arms, holding Kate between us, to begin the rest of our lives as they would be from now on, in the knowledge of what we had done.

SOMETIMES, WHEN I wake in the night, the sound of a shovel grating on shale in my dreams, I still cannot believe it. I have spent so long running from the memories, pushing them away, drowning them in drink and routine and everyday life.

How. The word rings in my ears. How did you bring yourself to do it? How did you ever think this was right? How could you think what you did was the solution to Kate’s terrible situation?

And most of all, how have you coped, living with this knowledge, living with the memory of that panicked, drunken stupidity?

But back then it was a different word that reverberated in my head all that night as we smoked and drank and cried on Kate’s sofa, holding her in our arms as the moon rose and the tide washed away the evidence of what we’d done.

Why.

Why had Ambrose done it?

We found out the next morning.

We had planned to stay the rest of the weekend, to look after Kate, keep her company in her grief, but when the clock that hung between the long windows showed four, she stubbed out her cigarette, and wiped her tears.

‘You should go back.’

‘What?’ Fatima looked up from her glass. ‘Kate, no.’

‘No, you should go. You’ve not signed out, and anyway, it’s better that you’re not … that you have …’

She stopped. But we knew what she meant, and that she was right, and as dawn began to break over the marshes we set out, shaking and nauseous with wine and shock, our muscles still aching, but our hearts aching harder at the sight of Kate, huddled white and sleepless in the corner of the sofa as we left.

It was a Saturday, which meant that when we crawled under our blankets, drawing the curtains against the bright morning light, I didn’t bother to set my alarm. There was no roll call at Saturday breakfast, no one checked us in and out, and it was quite acceptable to skip it and go straight in for lunch, or make toast in the senior common room, with the toaster that was one of the privileges of being in the fifth.

Today, though, we didn’t get a chance to sleep in. The knock came early, quickly followed by the scrape of Miss Weatherby’s staff key in our bedroom lock, and Fatima and I were still prone beneath our red felt blankets, blinking and dazed as she strode into the room, pulling back the curtains.

She said nothing, but her shrewd eyes took it all in – the sand-spattered jeans lying on the chair where I’d left them, the sandals clagged with mud from the salt marsh, the red wine stains on our lips and the unmistakable cherry-ripe scent of alcohol leaching out through the skin of two hung-over teenagers …

In the bed across from mine Fatima was struggling upright, raking hair out of her face, blinking in the cruelly bright light. I looked from her to Miss Weatherby, feeling my heart begin to thump in my chest. Something was wrong.

‘What’s going on?’ Fatima asked. Her voice cracked a little on the last syllable, and I could feel her worry rising in pitch with mine. Miss Weatherby shook her head.

‘My office, ten minutes,’ she said shortly. Then she turned on her heel and left Fatima and me staring at each other, terrified but silent as unspoken questions passed between us.

We dressed in record time, though my fingers were shaking with a mix of fear and hangover as I tried to button my top. There was no time for a shower, but both Fatima and I splashed water on our faces and brushed our teeth, me hoping to mask the worst of the cigarettes on my breath, trying not to retch as the brush slipped in my trembling fingers, making me gag.

At last, after what felt like an impossibly long time, we were ready, and we slipped out of our bedroom. My heart was thumping so hard in my chest that for a moment I almost didn’t hear the footsteps from above. Thea was hurrying down the stairs, her face white, her nails bitten to blood.

‘Weatherby?’ she asked, and Fatima nodded, her eyes dark pools of fear. ‘What d’you –’ Thea began.

But we were on the landing now, and a passing crowd of first years looked at us curiously, wondering perhaps what we were doing up so early with our pale faces and trembling hands.

Fatima shook her head, a kind of sickness in her expression, and we hurried on, the clock in the main hallway striking nine just as we reached Miss Weatherby’s office door.

We should have got our stories straight, I thought desperately, but there was no time now. Even though none of us had knocked, it was exactly ten minutes since we’d been summoned, and we could hear noises coming from behind the door – Miss Weatherby gathering up her pens, pushing back her chair …