It was the London Triathlon, Olympic distance.
It went alright, I didn't quite get the sub-2h30m benchmark though, thanks to a slow swim. I was rank 569 of 3773 with times:
Total 02:34:02
Swim 00:39:11
Bike 01:03:36
Run 00:43:53
So swimming was the weakest but also neglecting brick training of swim-to-bike meant I had jelly legs once I got on the bike.
One thing I have heard form several sources is don't fear the swimming part of an ironman. No idea if it is true but I spoke to someone who has done a couple and also asked around online. I always said I wish there was a triathlon that replaced swimming with something else like kayaking, ski touring, etc. Everyone seemed to say that people who come form cycling and running fear the swim, and runners under estimate the biking (that's me). On average swimming takes 10% of the total exercise time, and is over in around 1H15 minutes. If you are a slow swimmer and towards the back of the pack in general then maybe 1Hr 30-40minutes. That doesn't seem too horrific. You are also fresh, don't have digestion or dehydration issues yet, shouldn't get too hot, and have the initial adrenaline. The biking you do for like 6.5 hours and the running for 5 hours on average.
Being 5% slower on average at the swimming puts you less than 5 minutes behind. 5% slower at biking puts you 20 minutes behind.
The main issue for slow swimmers I was told is that poor technique will waste a load of energy which will then hit them by the time they are running, and likely before they hit the half way mark of the cycle.