It's 7.30 in the morning. I have just woken up for final time, having woken up roughly once every hour since midnight, each time thinking I've overslept, twisting in the darkness to read the glowing clock, in a panic. My thoughts are full of things that can go wrong with my visa application process. There are dozens of forms involved, each in triplicate. Will I have put "immigration" in the box that is supposed to say "employment"? I've left my home address blank because I don't know where I'm going to be living, does that make the form invalid? They have to take all ten fingerprints, and the website sternly warns that a cut or blister will lead to my appointment being cancelled in big red letters -- and my thumb is peeling. Will my passport-style photos, taken at Snappy Snaps at extortionate prices by a disinterested clerk, meet state department regulations (which can be worryingly detailed)? Will my credit card fail to work, as it's done several times recently, leaving me unable to pay the US$500 "fraud prevention fee"? Will my backpack be large enough to be considered a large bag, such as are not allowed into the embassy building? Have I accidentally answered "yes" to the question about being a former member of the Nazi party?

So I get up and get dressed, putting on my one and only suit: I was planning to wear just jeans and a t-shirt, but everyone and his dog said not to be crazy and wear a suit, so the suit it is. I'm wearing one of my flatmate's shirts, because I didn't have any ironed shirts and Murphy's law is very clear that if I iron a shirt the night before my fingerprints are taken I will accidentally burn one of my fingers on the hot iron and invalidate the whole process. It's still only 8.30, but hey, there could be a tube disaster that somehow makes it take 90 minutes to get to Oxford Circus from Stockwell on the Victoria line, a journey that ordinarily takes about 10. Hell, in 90 minutes I can walk there, giving me plenty of time to walk to the wrong building and queue in the wrong place and fail to find Grosvenor Square and the hundred other things I'm worrying that I'm going to do.

The tube journey seems longer than usual, but that's probably just because I'm not wearing my iPod: electronic devices are not allowed, mobile phones must be switched off, etc.. My watch has a USB cable, does that mean it's an "electronic device"? I mentally prepare to throw it away as a last resort. At Oxford Circus I stop and withdraw £300 in cash so that I don't have to rely on my credit card, and I turn up at Grosvenor Square. It's 9.15, and my appointment -- as evidenced by my machine-readable, bar-coded appointment form, in triplicate -- is for 10am.

The embassy was a large, ugly, and solid building before September 11th. Since then it has become encrusted in a now-permanent shell of temporary metal and concrete barriers, lines of security tape, tents, metal detectors and x-ray machines. There is a crowd of people outside, queueing in four orderly lines next to a sign saying "visas". A friendly British girl, younger than myself, dressed in a high-vis jacket and carrying a clipboard and a paper cup of coffee, asks to see my forms. She checks the appointment and asks to see my receipt -- another machine-readable, bar-coded document in triplicate -- demonstrating that I have paid my US$100 "visa application fee". It strikes me that there are about 300 people here, each of whom has already paid at least £60 just to be able to line up, netting the embassy a cool £18,000 -- probably this girl's annual salary -- before 10am. That's before the other people turn up and long before anybody has paid £250 for "fraud prevention" (apparently frauds are poor).

There are four parallel queues of people along the side of the building, getting progressively longer as they get closer to the building, apart from the closest queue, which is pretty short. These are for appointment times -- the queue right next to the barriers is the 8am people, the longest queue is the 9am people, and my 10am queue is already 30 people long at 9.15am. Most people are dressed heavily, many have children with them -- another requirement of the visa process is that all dependents must turn up for the interview. I note with concern that almost nobody has any kind of a backpack, even a small one -- most have opted for messenger bags and the more paranoid have opted for just a manila folder with their vital documents, or a plastic shopping bag.

At 9.30 the last of the 8am applicants disappears into the buildings and all the queues shift over by one. Everybody is cold. The guy in front of me is a young, attractive asian man, and realistically he probably has more to fear than most from the US visa application process, and he knows it. He is taking no chances: no bag, no electronics, and a very nice suit, but not anything else. In the next 45 minutes he begins to shiver. At 9.45 an elderly woman turns up and gets put into the 11am queue. I hear her call someone who I imagine to be her son or daughter: "yes, there are a lot of queues but I'm in a very short one, so hopefully I should get in quickly". She has not worked out that she will be standing here a minimum of over an hour, probably more like two. A small girl in the 11am queue pulls out her Gameboy DS, and a tinny chorus of tinkles and bleeps floats through the otherwise almost silent crowd. Lots of people glance askance at the DS -- are those okay? We could have brought our iPods! Secretly I hope the girl gets in trouble, so that my own music-less hours have not been in vain. But she's hours behind me in the queue, so I'll never know.

Round about 10am our queue gets folded into the stragglers from 9am, and I'm beginning to observe more carefully who goes in. Several people have already got in with backpacks bigger than mine, so that's okay. Nobody in the queue system has been turned away, although over the course of the last hour several people have not been allowed to queue, such as an 8am family who turned up at 9.30. As I get to the head of the queue, the guard checks my passport and my receipt, then sends me on to the security tent, where my bag is x-rayed and I'm checked for metal. The security tent is actually on the opposite side of the building to the visa entrance, so we walk along the outside of the building, inside the rows of non-temporary crash barriers, past the huge queues we were just a part of. I try to spot the old lady in the 11am queue -- it's 10.45, and the 10am queue still has several hundred people to go.

Inside the embassy it's blissfully warm compared to the 9 degrees I've been standing in outside. A friendly man ensures that my phone is switched off and sends me through a heavy auto-locking door into a waiting room that's big enough to hold at least half of the people currently freezing their asses off outside. I get given a number, and enter a queueing system like the one at Argos, where you see your number at the end of a queue of numbers on a set of big overhead screens. As feeling returns to my fingers and toes, things are going much faster: my number comes up in 10 minutes. I go to one of the desks, which is more like a bank counter: you stand up and talk to someone sitting behind bulletproof glass. It also happens to be the wheelchair-accessible one, so it's far too low for me. I stand in a half-crouch while a friendly British man asks for all my forms and papers and begins to stamp things. He fills in my missing home address for me with "San Francisco, CA" and takes my fingerprints via a scanner built into the desk. He tells me to go to another desk to pay my fees, and to wait for my number to be called again. I don't even notice that he's not given back my passport.

The girl at the cashier desk is a bit startled that I want to pay in cash, but it's no problem, and she rings open a dusty cash drawer and gives me my change. Now I have to wait for my number to get called again, but this time it doesn't appear on the screen queueing system. Since everybody is getting different types of visas, and they all take different lengths of time, the numbers being called for the second time are called in random order, so you have to pay close attention to every announcement. You can tell whether a number is being called for the first or the second time because the first-timers get called to desks between numbers 1 and 11, and the second-timers to a second bank of desks, 13-22, which are down a short corridor away from the main room (desk 12 is the cashier).

It's only 11.15 when my number is called again. Desk 20, it turns out, is the only desk you can see as you walk down the corridor: it's rather like the long walk to the principal's office in some American high school movie. It's another glass-screen arrangement, and a rather older gentleman, this time an American, smiles and asks me a few questions: his job, apparently, is to make sure that I know what I've said on the forms. Who am I working for? "Yahoo," I reply, but he's only heard the "hoo" bit and thinks I'm repeating the question. What's the company name, he asks, louder this time, and this time he gets it. He asks where I'll be working: I say San Francisco and he frowns; that's not what the form says, of course, so I quickly modify to "Sunnyvale, which is near San Francisco" and he starts smiling again. Close one. He asks if I've made travel plans: I'm prepared for this one. It's against the rules to make any travel plans before I get the passport back with the visa inside it, so I answer truthfully that I'm waiting for the visa before I do anything. He smiles, and that's it: he tells me they'll be giving me my visa -- something everybody said they wouldn't tell me -- and to expect it in 3 working days, with 3-5 working days on top of that for delivery.

I stop and make arrangements with the courier service to have the passport delivered, and then it's over, and I'm outside, suddenly exhausted from the tension and the lack of sleep. But that doesn't matter, because it's done: I'm going to America, and I'm going to be there for years, and there's nothing stopping me any more. For better or worse, I am an American now.