My parents always taught me to get the oil (or dripping/lard in their case) up to the correct temperature before adding the chipped tatties. I await the outcome of your test ummmmm but I won't hold my breath.
But in Nigella's defence, her recipes do tend to work....unlike some other well known chefs I could mention (Yes, I'm talkin' about you Jamie Oliver).
I like Jamie Oliver, I like his throw it in roasting tin and hope for the best approach. Nigella, to me, is like watching my aunty come on to my boyfriend at christmas.
Apparently it can take up to an hour cooking them from cold oil though
its not supposed to go to a high temperature... iono what her method is though, Ummmm. Speaking of chips, whats the big deal with the thrice cooked chips?