Bag B is done. After work today (and after struggling back to Spencer Alley through yet another rainstorm) I attached the handles and finished the lining.
These crisscross corners were new to me. They would be an easy and effective technique to remember for the future, if memory were reliable.
And now the vintage Eighties coat (which looked like a goner when photographed in shreds two days ago) is striding into the future, inhabiting its new body.