AI -
Yes, it is generally easier to cycle in the dark if you know the area, as familiarity with the route can help you navigate and anticipate potential hazards, even with reduced visibility, according to Kwik Fit and Cycleplan. Knowing the route allows you to anticipate turns, understand where the road is uneven, and mentally prepare for any obstacles.
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He was brought up and worked at WHF and lived at GH. So would be familar with The Sea Wall route.