Not sure about the specifics at Chester, but all of the north TfW conductor depots are similiar:
Shift pattern is a 4 day week:
Begins on a Wednesday with 6 or 7 lates*,
Wed/Thu off,
6 or 7 earlies*,
Fri/Sat/Sun/Mon/Tue off,
and then repeat every 3 weeks.
*6 or 7 depends whether you have a...