MJ- Here's the story as far as I know it.
As an event the TGO challenge started back in 1980 and Hamish Brown was the man behind the concept, the Challenge has received TGO magazines supported since then.
My understanding is that the Challenge as an event is restricted for environmental, safety and administrative reasons to 300 participants each year, plus a number of people associated with the event. There's also numerous volunteers "backstage" who give their time freely, ensuring the Challenge cogs run smoothly, from vetting routes to making bacon butties and staffing the control centre. It is also renowned for its sociability and camaraderie, and you will always find your fellow-Challengers willing to help in any way they can. If the event is too big or small this magical bit won't really happen! But as Mike points out you can do it yourself at any time, its just a different experience and that has its own merits too. Its all about walking your life and being out there.
Roger Smith is the main man to talk to, a TGO Challenge Jedi Master. He's the event co-ordinator and you'll get a lot more sense from him.
Cameron you naughty tinker, you've got me all excited at the thought of it! Just a few weeks to go until that coveted October issue hits the news agents shelves. The wife says I can go if I'm able to take my Llamas. Does Roger have rules about Llamas on the Challenge???=]