While doing the Islington mission (with gasmask), I had to get past the Millers gang.

There comes a point when you find two dead tommie's in front of a gate. I stripped one and turned to strip the other at which point the game crashed.

I Noticed the save was from a little earlier so tried to load it but it crashed the game again.

Apparently, its damaged ALL the saves.

Definatly not, apart from the chance that your system drive could have a problem (and i have no clairvoyance ball here).
Did you try to start the computer completly new (not just a sleepmode or whatever), when the fallout 4 engine crashes there is a chance that bugged stuff remains in the memory and then buggs over and over again when you try to restart it.

Restarted PC and tried again. It appears to bug the autosaves (I tried several) but not the manual saves.

i had a same problem,thought itt crash my saves completely,but i just skipped this part,seems like that only east part of location is buged,so i just entered from south gates and run straight to quest location without any saves problems