Running

BGR, funnily enough, is not a day trip. You need to spend a lot of weekends recceing beforehand to learn the route - it probably takes a commitment of about a year, esp if you're London based.

You also need a strong support crew, with runners who will witness you on each peak. A friend did a solid finish with hours to spare, but it wasn't recognised as one witness broke and couldn't make it to the last 2 peaks on his leg.
All true^

Don't know how a runner of Jurek's quality only just managed to break 24hrs.

because he was taking pics and tweeting some of the way round?