Can someone tell me what "a good level of fitness" is?

I suspect that the phrase "a good level of fitness" is used to get event organisers out of a hole if things go wrong. Trouble is there are no simple and quick assessments that are at all reliable. Fat people might be very fit. Thin people might be on death's door. There's a rough and ready fitness index that gives a fairly objective numeric result and has proved consistent when I've used it over time.

Have a stopwatch, paper and pencil ready. Finish your vigorous exercise. Immediately lie down flat and start the watch. After one minute count your pulse for 30 seconds. Write it down without moving much. Do it again after another two minutes, then again after another four. Add up the three numbers. Divide 15000 by the answer. More than 110, excellent; 95 Very good; 88 good; 81 average; 75 fair; 71 poor; less 'make a will'. This wouldn't be practicable to test people on an event, but might be worth suggesting to them if they are unsure.

Not being a fat wobbly wheezing lardarse... at a guess.

There are so many variables - distance, profile etc. I think if you were to try to find a definition it would probably focus on:

1. Having regular weekly exercise (there are Health Dept guidelines about daily physical activity), possibly including cycle-specific exercise at least in the run-up to an event and
2. Not being morbidly obese, in the clinical sense.

I assume it's there just to cover them legally and morally in case someone who has spent 25 sedentary years smoking, drinking and eating crisps suddenly decides to ride London to Brighton and ends up shuffling off their mortal coil.