I had left a whole turkey neck (probably about 7" in length) on the side for one of my adults and I nipped into the lounge to take hubby a coffee and when I came back my 5 mths old large breed weighing about 28kg at present had run off to the end of the garden with it and as I tried to approach she swallowed the whole lot!!! No chewing just swallowed it whole like a pelican with a fish. Up until now her leave command was second to none, but obviously a sneakily stolen turkey neck was far too good. How dangerous do you think this is?

I wouldn't worry  personally, I feed raw and necks are no problem, If she swallowed whole you might see it back again fairly soon, at which point I would expect her to try again! dogs can be fairly manky but regurgitating for a 2nd attempt is pretty harmless.  28 kg is pretty much the size of my labs and they eat them no problem. If she's still got baby teeth she might struggle to chew it possibly but necks are quite soft bones.

my pups of only a couple of months old eat these so I would not worry about it.

I think this might have been a blessing in disguise as you have discovered her leave command is not "second to none" but "effective only if the temptation is insufficient"

If you ordered me not to touch my brussel sprouts that would be easy; to keep my hands off my Hotel Chocolat? No chance! LOL

Well so far no signs of anything untoward. She is as nutty as ever and hasn't brought it back up and ate her breakfast with as much vigour as usual.

I wouldn't worry too much. I once had a 4 week old pup swallow a whole chicken wing. The others were mouthing and chewing daintily on theirs but this one, took it and just like yours, swallowed it like a pelican. I was having kittens and making frantic phonecalls to fellow barfers. Just as they said, it was fine and several years later he is still a greedy dog who never chews his food just hoovers it up.