Defying gravity, Paget managed to pull himself back into the saddle, coming home clear but with two time penalties.
Caroline Powell and Boston Two Tip is in ninth place, while Todd is in 15th position. Lucy Jackson riding her first Burghley was over the moon to finish in 42nd spot aboard Animator II.
The Captain Mark Phillips-designed course challenged even the most experienced riders, with the sticky ground making it particularly tough for the horses.
Leader Sinead Halpin could be the first American in 19 years to win the prestigious event after retaining her overnight dressage lead to stay in front.
Today's showjumping round promises to be heart-stopping. FEI Classics leader William Fox-Pitt (GBR) aboard the Kiwi-bred Parklane Hawk - who won Burghley last year - is just behind Nicholson.
Just 56 completed the cross country, nine were eliminated, 16 retired and four withdrawn.
Rotorua equestrian Craig Nicolai withdrew before the event with his horse Just Ironic being injured.
Meanwhile, New Zealand Paralympian Anthea Gunner and Huntingdale Incognito have finished 19th in their grade two individual test at the London Paralympics, scoring 63.762 per cent - a 3 per cent improvement over their first outing at the Games.