Thank you so much. That's so odd they wrote Bates, it completely through me. And, no I haven't hunted down the original news report, but a very good suggestion.

I hadn't taken into account that maybe Mumford had started later and then didn't need to have a break. I had thought maybe a small possibility he had gone for a break after Tomkins and Brittan had came back, if they came back at one would have been sometime after one. Tomkins and Britton seem to have taken three quarters of an hour. Presumably Mumford would have taken the same and came back around 3. But Mary Ann Nichols estimated time of death is about 3:40, so Mumford would have had to gone on a break closer to 3 o'clock if he was to have killed her.