Are we talking cramp in the torso or in the legs?

If it's legs, then I agree with Stolly. It's usually brought on by running outside your training, either in pace or distance (or both).

I was nowhere near as good as roadrunner, but my PB was 2:30 and I've done 27 marathons under 3 hours. I never took any food on board during a race and breakfast on race day would be one slice of toast and 2 cups of coffee. My food was already in my muscles, I reckon it's asking for trouble to divert blood to your stomach when racing at speed. It often makes me want to faint..

Neither did I use any sports drinks, I would just take water and, unless it was exceptionally hot, most of that would be thrown on my head and thighs to cool down externally. I suspect in most races I drank less than a pint and a half. Again what you need in the race should already be in your system. (AL fell races are quite different, there I certainly need both food and water in my stomach.)

The only cramp I suffered in 20 years of marathons was a stomach cramp in 1981 caused by swallowing water the wrong way and coughing violently. The ascent of Whernside in the 3Ps is a completely different matter, my calves always throw a little flutter up there, because I'm working outside my training.