The weather forecast for that week was awful and 3 March was foggy, plus there was drizzly rain and some heavier showers (at least in London, I remember because I chose to run indoors rather than go out in it).
IMO going by car instead of on a bike in winter generally, or just when the forecast is bad, does make some sense. It'll be for investigators to establish demonstrate if hiring a car was a departure from his usual travelling patterns, and for the defendant to show if there was an anodyne reason for whatever he did icw cars