I totally agree with you David but nobody that has any salt is going to leave a site being more dangerous than when you arrived there.
I've just watched it again. He finds a gas bond and a suspected water bond disappearing a 'pile of rubble'.
The loop tests are returning 37 ohms.
The CU is a complete joke, including two unused RCDs, and the bus bar is running into both sides on an unused RCD. There is nothing to give any confidence that this was any kind of compliant installation once, and all bets are off. It's a metal unit with no tails clamp, and no insulated tails gland.
In many properties I'd be happy from the clues present to assume there's a TT electrode that I can't find. In that one I wouldn't be, and I'd be worried (as I think Del was) it was an old water pipe earth.
Regarding the TNS connection - he said in the video at the end "this is just temporary" and leaves with a Zs of 0.85 ohms. One assumes that his "temporary" comment means there was a plan for more work.
Phoning the DNO on this won't help much. In this situation they would just say there is no evidence they supplied an earth, and the choice would be paying for a new PME supply (cost variable from 0 to £4000 as per the darts-board of the day) or installing a new visible electrode and making it
look like a TT install. Either way a new CU looks to be required. So realistically until Del had time for a larger job and some choices were made it was going to stay with no verifiable earth for a week or two at best.
I not actually sure what I'd have done in that situation, it would depend how much time I had and what I had with me, but I do understand why he did what he did, and I don't consider it more dangerous than when he got there.