How about one fast group and one slow group. Slow group waits for stragglers. People who can't keep pace with fast group join hippy at the pub and raise a glass in a big "fuck you to this cycling bollocks" kind of way. Aim for a date near summer solstice to allow plenty of day light. Early-ish start.
We don't have to worry about light so much as it warms up, daylight shavings and stuff. I still prefer an early start, 1) to avoid traffic through and out of London and 2) contingency in case we do take far longer than expected.
We don't have to worry about light so much as it warms up, daylight shavings and stuff. I still prefer an early start, 1) to avoid traffic through and out of London and 2) contingency in case we do take far longer than expected.