My carry list seems pretty minimal compared to this. On a summer 200-300km audax with no bad weather expected I go very light, really no more than if I was on a club ride.
Small saddle bag = 2x tubes, some instant patches, multi-tool with chain tool, tyre boot, a few chain links, speed chain link, a few zip ties.
Pockets and/or small top bar bag = a couple of 9 bars, Vitamin I, a light luggage lock, gilet if it might start or end cool.
On the bike = pump, lights if required.
Anything else to eat I'll get on the way round unless I'm planning a quick solo lunch stop when I'll stick a few jam sandwiches or malt loaf in a pocket.
On a winter 200 I tend to take more food (often malt loaf and some chocolate) and a change of shirt, socks and gloves if it's wet. Waterproof shorts if it's very wet. Usually 3x or 4x tubes. A bulkier lock as more likely to be indoors away from bike. Emergency spare front and rear light. I use a Carradice Audax Super C on my winter bike and a top bar bag for easy access to rations. Lights and pump are on the bike anyway.
Useful to see what others take, I've gained a few tips from this thread!