It was agreed that as Daylight Savings finished, the start time of the Monday afternoon ride should move back to 3pm. If left at 4pm some riders may soon be riding home in the dark.
PS. On the topic of cyclist visibility: see the study below, comparing expectations against reality.
Study in 2012 by Wood et al at Queensland University of Technology
The third chart shows Estimated vs Actual, with ways to increase the distance at which we're noticed by drivers. It's the right time of year for us to make these improvements.