Sometimes it's the sheer stupidity of some people that astonishes me. Mainly my own, in choosing a job that stops me ever seeing my friends in return for a boatload of abuse off the public every day. But also my registrar, for thinking he's the hardest man in the universe.

"Just get the laughing-gas mask back and boot him out. He's a skag-head." It's important for you to know that my registrar only ever deploys street slang like this with an ironic smirk on his face, in order to reinforce his image as the hard man of emergency medicine. And it is, as ever, an astute assessment of the clinical situation.

Because the extremely smelly man in the next cubicle, who looks very much like a heroin addict pretending to have renal colic, is not the one-in-1,000 genuine punter we always diligently check for but, in fact, another heroin addict pretending to have renal colic: what is more, he couldn't even be bothered to learn the story properly. And the A&E sister recognised him as a repeat offender. And he has ID in his pocket for the name she remembered him by.

This man isn't just a crap actor. He has been actively mocking me, and he thinks he can get away with it, for the simple reason that he is twice my size. He also won't give the nitrous mask back, even when I use my special doctor's voice. The nurses are suddenly too busy to help.

"Fine. If you all want to be pussies about it, as usual, then I'll go in there and be nurse, security guard and registrar, shall I?"

My registrar flounces off.

"Lord Earl to see you, Dr Foxton." Sister curtsies. Lord Earl is an elderly homeless Rastafarian who smells of urine and comes in about once a week when people beat him up for fun, because you are fundamentally a pretty sick bunch out there. That is all anyone knows about him. Just ask the social workers about it. This is A&E.

"All right, Earl?" I say.

"Irie, doc."

He is carrying a bunch of rags in front of him. "Take a seat."

He hasn't even been through triage, but everyone is nice to Earl. It's traditional. He just walks in and helps himself. "Might have to lie down, doc."

"Right you are, Earl," I smile.

He pulls away the rags.

"Got a bit of a problem this time, doc."

He's a dead man. I think I can see bowel hanging out through the blood. I press on the hole and shout for help, and hear my registrar roar in reply. It turns out that he had pulled the nitrous-oxide mask off the junkie, leaned over to turn the tap off, and then felt a jaw dripping in HIV-laden saliva clamping down on his ear. "I want that fucker arrested right now," he whispers into sister's ear as we call anyone we can think of to A&E to sort out Earl.

In four days I'll be a psychiatrist. Which I reckon I'll be pretty good at. So seven hours later, at one in the morning, a 17-year-old French exchange student potters into A&E talking bollocks in an outrageous French accent. "I feel so strrrange. I can't explain it, everything feels just so unreal."

The triage nurse has already warned me that she's not going to shut up about it and go home. "It's just all, so much more detail, and my heart is racing and I'm caught in my thoughts and other people and every possibility must be calculated for every..." All right. This is not an existential counselling service.

'Can you think of anything that might explain it?" I ask, patiently. She starts to giggle. "Well, it's another thing. I..." She giggles uncontrollably. She can't even open her eyes, let alone patch words together. "Where have you just come from?" I ask, bored senseless.

"... party!" She squeals, and bends over crippled with laughter.

"Did you take any drugs there?" I try to look like nobody I know has ever even thought about taking drugs, yet chilled enough that it is OK to tell me.

"No." She laughs. "Oh, my God," she grabs my arm and nearly falls off the trolley. "But I ran out of cigarettes and somebody gave me a roll-up cigarette." She takes off her sunglasses. Her eyes are blood red. She squeals with laughter.

"Are you feeling hungry?" I sigh.

She stops laughing and stares with immense gravity. "Merde! Do you have any popcorn?"

I can barely be bothered to write in the notes. "You're stoned," I smile. "Just go home."