You can't just set off from San Francisco and hope to run all the way across America without having done any training first, unless you are Forest Gump.
In order to gain the stamina required to push out endless 40 mile days without getting injured, we came up with a rough plan, which may be of interest in case you are thinking of following in our footsteps...
Here's a few things we did:
1) Run high mileage for several consecutive days, to see what happens.
2) Run from Sheffield to Cranleigh in Surrey.
3) Run some ultra races.
4) Do a couple of Bike Races (Steve's idea)
5) Run round the Lake District for 3 days (Steve again)
6) Run some foreign marathons (Madrid, Lisbon, Seville) (Another of Steve's ideas)