Re Fanny Mortimer: "I was standing at the door of my house nearly the whole time between half-past twelve and one o'clock this (Sunday) morning, and did not notice anything unusual."
Notice the "NEARLY THE WHOLE TIME" in her statement. She had a sick husband and I believe it was five children to deal with. So clearly she was not at her door THE WHOLE TIME.
There are two different versions of Mortimer's account. In one version she says she went outside shortly after hearing the "heavy stamp" of a policeman pass by-I believe this would have been around 12:42-12:43, meaning she arrived at her doorstep at about 12:45. She then stood at her door for no more than 10 minutes before returning inside. About 4 minutes later she heard Louis' pony and cart.