"His blood pressure's dropping, we may have to amputate." The paramedic looks up at me. I'm standing there, bruised, battered and terrified, but alive, all because my partner has quick reflexes. And he's paid the price for trying to keep me safe.

The paramedic is asking me to make a decision which will affect the course of my partner's life. He's asking me for permission to take my partner's right leg off just above the knee.

"No," I shake my head, not so much in the negative as trying to clear from my head the mental image of Stuart Turner, permanently crippled because I gave in too quickly. "Please...," my throat is tight, and I choke over the words, "please try. Stuart's strong." He would want me to fight for him.

"If he drops any lower, we'll have no choice. If we amputate, we can save him."

Put in those terms, it sounds so rational. Such a simple choice. Cripple my best friend for the rest of his life because it's the rational choice. Hang on for longer, and risk his life.

I shake my head again. This time it's to cover the fact that I'm shaking like a leaf. I know Stu. It's only now, standing, watching them tear Sierra Oscar Five apart to free him from the wreckage, I realise just how much knowing the man who's my best friend really counts. And the effect it has on me. Because I know him so well, I know he won't cope. So much has fallen on his shoulders in his life.

How did we get here? I shoot a glance across at the rest of the team, at the top brass standing about. I'm seeking out one face. Perhaps it isn't fair to land it all in her lap. But her choice of position put us right in harm's way. Both of us had argued we were in the wrong place, but it was her decision.

It was a box van, weighing in at roughly seven tons, many times the weight of the Toyota. It was running straight at us. Stu flicked the key and the car's engine burst into life; he threw the gear box into reverse and his foot slammed down on the accelerator. We were flying backwards, and then we were flying sideways.

Everything was hazy. I could hear shouting and the sound of running feet. My entire body hurt. I groaned and turned to Stu. It was then I realised his evasive manoeuvre had saved me at his own expense.

Someone hauled the passenger door open, and hands started to check me out. I pushed them away and scrabbled for the seat belt. As my shaking fingers connected with the button, someone must have cut the seatbelt because it fell away from me. I pushed the remains of the airbag out of the way and leaned towards my partner.

"Stu," I whispered.

His eyes opened and he looked at me. I've been a copper for twenty-three years, and have never before seen that much pain and fear in a man's eyes. His lips moved. "Help me," he whispered, his left hand reaching for my hand.

We held onto each other as I prayed for an ambulance and paramedics. I got both. But there was no relief.

He was in a bad way, and I knew it. I didn't need someone to tell me. I didn't need to be asked the question. We had made each other designated decision makers in case of disaster. Stu didn't want his sister to be in that position, and I had agreed to do it.

I never believed that something would happen. I never believed I would be standing beside the wreckage of Sierra Oscar Five and have power over Stuart's future.

I stood and shivered as heavy machinery whined and sparks flew. Watching as they worked to keep him alive and free him from the crushed car. His right side had sustained terrible injuries. His shoulder was dislocated, his collarbone was broken, his arm was broken as was at least two of his ribs, he was bleeding internally, and his leg was badly mangled.

Then suddenly they made it -- the last cut -- and he was free. I folded my arms across my middle and followed the stretcher to the ambulance. I sat in the corner of the ambulance as they fought for his life all the way to hospital.

A nurse was pressing me to get checked out, but I had assumed responsibility for my friend. I have no idea how long I sat there waiting. It didn't really matter; I would see this through, because there was the promise we made to each other and that question hadn't just gone away. It was still hanging over us. I wanted them to save his leg if possible, of course, but if it came down to a final choice, I wanted him alive.

I drank cups of warm brown stuff which might have been coffee, and tried to still my shaking hands. I tried not to imagine the worst. But if I closed my eyes, the whine of machinery, and the flying sparks, and the look in Stu's eyes just before he lost consciousness, all haunted me.

"DC Masters?" The voice was calm, reassuring. I looked up into a kindly face and promptly burst into tears. The surgeon tried to explain all which had been done and how much more was needed, but Stuart's battered body could only take a little at a time. They could have fixed all his injuries at once, but they would literally have operated on him to death. But the real killer was that they couldn't save his leg.

I knew Stu was strong, holding onto life; he would fight, even with his right leg gone just above the knee. That was Stu all over: a stubborn refusal to accept defeat, but how he was going to cope with this I had no idea.

They let me sit with him for a while. He was heavily sedated and swathed in bandages. They had staunched the internal bleeding and put back his shoulder. Then they'd completely immobilised his shoulder and arm, surrounding him with pillows to keep him still in the bed. I eased the plastic visitor's chair up close to him, so I could take his left hand in mine. I tried not to look at the stump, supported by a pillow. The cost of me--hale, hearty and whole--sitting there next to my best friend, was the loss of his leg. Honestly, even now I'm not sure whether I was trying to reassure him that I was there for him, or reassure myself that he was still alive. Survivor's guilt, I suppose.

His fingers did close around my hand, though, so I was glad I'd done it. He knew, on whatever level he could, that I was there for him.

After I was certain he was asleep, I went to do the hardest thing I'd had to do in a long time: tell Jack Meadows that Stuart Turner's career as a frontline officer was probably over. I tried not to break apart, just deliver the bare facts.

I couldn't think about the implications, about the decisions, about Sun Hill, about anything else than being there for the man who had saved my life.

They granted me compassionate leave, and in the days that followed I did a lot of sitting, hand-holding and worrying. He was strong and stubborn, but he was also very seriously injured, giving me a couple of scares along the way.

As Stu's decision maker, I had access; as his partner I could no more have left him alone to face this than flown. His sister came as often as she could. She was devastated, but between us we worked out how we were going to tell him.

It was four days before he was sufficiently lucid to question what was going on. I told him the truth as gently as I could. I watched him cave, I held onto his hand as he fought for control, then I kicked off my boots, slipped up onto the bed next to him and put my arms around his neck, and he just dissolved into me. I rested my cheek against the top of his head, whilst his tears soaked the front of my shirt, and wished there had been something I could have done to prevent it.

Finally the flood's over. He's burrowed against me. He's weak, exhausted and hurting. I don't do men. I'm gay. But I gently put my fingers under his chin and tilt his face up. We just look at each other for a second. And then our lips meet.

This isn't about sex. It's a promise. We need each other, Stuart and I, and I'm not going to desert him.