Cramp

Other than electrolyte imbalance, cramps can be caused by your muscles running out of fuel, though if they came on after only 32 miles that is unlikely in your case.

The fitter you get, the less likely you are to suffer from cramps, so there may be something you can change in how you train to make them less likely.

i can highly recommend Hammer Nutrition Endurolytes. I suffered terribly from muscle cramps and had tried a variety of different electrolyte replacements with no real improvement over the years. these are the first ones that i've seen a noticeable improvement and 5 sportives later this year I've yet to suffer any cramps. General good hydration as Dave says are important especially in this hot dry summer we've been having

Try bananas too, high in potassium.

yup, that's the first thing to try: electrolyte tabs, to replace salts.

athletic cramps are often the result of a sodium-potassium imbalance in your body which affects muscle function. if you lose a lot of sodium when you sweat (ie your sweat is especially salty) then replacing sodium is the priority. in some people it's a deficiency of potassium rather than the other way round, and electrolyte tabs don't tend to be so effective. bananas are good though.

Also, make sure you drink plenty of water. If you're using gels this is especially important as the concentrated glucose can draw water from your body to absorb the glucose, and dehydrate you.

Never been affected by cramp myself which might be due to me drinking Nuun and ?High 5? in my water which replaces the salts and electrolites lost from sweat.