I was wearing my helmet, but I don't think it actually did anything useful: the only effect seemed to be to pivot my head around. I wasn't using my helmet camera for that journey (I need to repair/replace it), which is a pity because it probably would have made quite an exciting video.
I didn't fall off the bike, but I unclipped my feet from the pedals and got off by myself. I later discovered that my chain had derailled itself, presumably related to the impact. I moved off the road and did my best to assess the damage. I could feel blood dripping down, and it's splattered over my panniers, glasses, and gloves. I have a mirror mounted on one side of my handlebars, so I peered into that and I could see that there was a cut above my left eye. My forehead also felt a bit puffy around there, although that seems to have settled down now.
I stood there for a couple of minutes, but the lorry driver didn't come back to investigate so I assume that they didn't actually notice the impact. Given our difference in mass, I probably didn't move the lorry at all and the driver may not have heard the crash if they had a radio on.
When I go cycle touring I carry a first aid kit with me, but I don't normally bother on my daily commute. It's also a bit tricky to deal with facial injuries when I can't see what I'm doing. In lieu of a bandage, I made do with a handkerchief, although unfortunately this was one that I'd already used to blow my nose so I just did my best to find clean(ish) sections of it to dab at my face. Running through the checklist for head injuries, I vividly remembered the impact (i.e. no loss of memory), I didn't pass out, and I didn't have any blurred/double vision.
I wheeled my bike along for a while, then popped into the first newsagent I saw to ask whether they sold plasters. The shopkeeper dug around but the only ones he could find were the fabric type (which I'm allergic to). Another guy was in the shop at the same time, and he advised me to go to Hammersmith Hospital, since that was only a short distance away. In a situation like this I feel a bit guilty about wasting people's time, and I certainly wasn't going to call for an ambulance, but I figured that it was probably prudent.
I wheeled my bike the rest of the way, because I wasn't quite confident about riding it, then locked it up outside the hospital. When I went in, the guy behind the reception desk was talking to a colleague. They both looked up, and visibly reacted. They didn't quite recoil in horror, but there was certainly an element of surprise there, as if I'd leapt out and shouted "Boo!"
Apparently it was very busy tonight (more so than average) and they only had one triage nurse on duty so I was warned that I might have a long wait. That's fair enough, and I wasn't going to complain (unlike some of the other people waiting). However, the guy on reception was able to jump me ahead by phoning the person who was handling minor treatment and asking him directly whether he could see me. Effectively, the receptionist was able to triage me himself, since it was blatantly obvious what was wrong with me. So, I only had to wait about 15 minutes before I saw someone which wasn't bad at all.
When I went in, the doctor (?) cleaned the wound. I've done this several times before on SJA duty, but it's a bit different to be on the other side. When I'm doing (either for myself or someone else), I can see what's happening as I go along, and typically I find that the actual wound is much smaller than the blood-smeared area. In this case, I couldn't see anything, so I had to wait for him to tell me what was happening. He put some iodine in the wound, and warned me that it would sting a lot; I braced myself, but it turned out not to be a big deal. I was aware of it, but since the wound was already stinging it was only an incremental difference. On a pain scale of 0-10, I'd say that it went from 3-4; on a scale of 0-3, I'd say that it stayed at 1.
After that, he glued the sides of the wound together and then put steri-strips on it. So, it wasn't deep enough to need stitches, but it did need more than just a plaster, which justifies my trip to hospital. He said that I need to keep that area clean and dry for 10 days, so this delays my swimming plans. I may also stay off the bike for a while, to reduce the risk of getting caught in the rain. I don't need to go back to the hospital (I can just take the strips off myself) so presumably the glue will disappear by itself. The wound is basically along my eyebrow, so there shouldn't be any visible scar. It looks quite swollen at the moment, but I don't know how much of that is from the wound and how much from the treatment:
There's no obvious damage to the bike, but it's overdue for its initial (free) 500 mile service so I'll book it in for that. In particular, I have to pull the rear brake lever all the way back before that wheel stops, so I think that cable has stretched a bit; that's normal (hence the service) but if it stretches any more then it would be dangerous.
I wonder whether I could have done anything differently in the moments before the crash. More precisely, I wonder what I could do differently in the future if it happens again: I'd rather plan ahead at my leisure than have to improvise on the spot. The only option I can think of is to throw up one of my arms in front of my face to absorb the impact, a bit like a breakfall in judo. The snag is that I'd have to let go of the brake in order to do that, so the bike would immediately start to accelerate. Is a fast impact on the arm better than a slow impact on the face? There's probably some optimal point in between.
Anyway, this collision was my own stupid fault, so please learn from my bad example: if you're driving or cycling, remember to leave enough room between you and the vehicle in front.