This fantastic video was recorded by Mark Bevan of Basingstoke & Mid Hants AC at the Pen y Fan Race in 2013 - it really captures the experience. It also reminds me what a hot day we had - especially poignant since only a few hundred metres away those SAS reservists were getting into big big trouble.
For those using this as a guide to the race, note that Mark and the others around him took a descent line of questionable merit from Pen y Fan. Instead of descending direct down the steep part of the slope, they went way further right, taking the diagonal route across the slope. This may appear more direct on the map, but in practice it spends more time on steep ground, and involves an extra stream crossing and minor rise before re-joining the outward route above the stile.