Question Author
Right, now give me a 5 min start to leg it........
They each take a sheaf of wheat, go up to the north end of the field, set alight to their sheaf s of wheat. They then go back to the middle of the field and start a new line of fire from east to west.
Half an hour later, the first fire has reached them......but they just walk over the already burnt out wheat where the second line of fire is now 50 feet away, just about burning itself out at the south end.
Result, they are completely safe...........though the Farmer will not be pleaseed.