Crazy idea, but it'd tempting to DIY this one for the Spring Bank Holiday.
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Start at Exeter, controls at Axminster (45 km), Lincoln (385 km), Humber Bridge (443 km), finish at York.
The route is pretty simple - Fosse Way, then Ermine St.
Departing at 6am on the Saturday would mean hitting the A303 section at before 10am, Bath at around lunchtime. The A429 around Cirencester is 160 km in, so around 4pm. Leicester is the 300 km mark, so before 3am on Sunday. It's then an early morning dash up the A46 to the 2nd control, Lincoln, 9am on Sunday. Should be a decently quiet DC dash. The A15, before minor roads to the Humber bridge, around lunchtime, then finishing in York at 5pm.
I'm sure there's a more scenic route, but charging across the country in the wheel ruts of roman chariots is kind of my idea of fun. And I think the slow audax timings are pretty ideal traffic wise.