I came across and interesting article recently about the issue of standard time in 19th Century London. Until the mid-century time was a very elastic thing and only began to be standardized when the railways got going and people needed to know about schedules. Apparently local time--the time you have on your watch and I have on mine--only really started to standardize around the time of the killings. It's unlikely that the brewery clock that Mrs Long describes hearing was set to GMT. It's also unlikely that Albert Cadoche's alarm-clock was set to the same time as the brewery clock. There could be a significant variation here. Enough for Mrs Long to see Chapman at around 5.30 am and Mr Cadoche to hear something untoward next door at around 5.20 am and yet still the sighting could precede the hearing...