In reply to ACollins:
It's a challenge not a race (other than against the clock), there's no set time to attempt it, it's up to the individual to organise everything themselves but there is an annual Dark Peak "train"where that club sets things up for a few of their members.
Basically the BGR was part of the 24hr fell bagging challenge that was popular in the early 20th century which had as its aim: "
to traverse on foot as many mountains over 2000ft and return to the starting point within 24hrs" (These days the required starting/finishing point is the Moot Hall in Keswick). It just so happened that Bob Graham's record stood for a long time and is of a difficulty that puts it just at the right point for the modern club fell runner, the Goldilocks zone as it were: not too easy that success is certain but not too hard that only the very best will succeed. Last year for instance there were 56 successes out of 144 attempts so slightly better than 1 in 3 but some years it is closer to 1 in 2.
The basic stats are 66 miles and 26,000ft of ascent/descent though both depend on the exact route taken.