I hope that your local Authority has this foolish waiver in black and white on official company paper!! Since when does the DNO hold sway over fundamental safety, emergency, switching arrangements??
No, not unless you can provide proof!!!
Again, who is the person responsible actually instructing you to depart from BS7671?? Is he, or the authority taking the full legal and/or civil responsibility for this safety omission instruction, or are they going to pass the buck on to you, if or when that safety omission contributed say, to the loss of life and or the building??
To both of you, ....get an official written instruction my friends, and keep it in a long term safe place!!! lol!!
I still have around 12 to 14 written instructions, which i have insisted on, for work carried out against contract specifications over the years. One of which, came in very handy long before any court proceedings ensued!!!