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Did they use a turbo on their breaks? Guess they did whilst they were eating/drinking/etc.
https://www.strava.com/activities/613997306/analysis
Look between laps 12 and 13 as an example. There's a section that's 8km long (130.8km to 138.9km) where they're static in the Roehampton car park, no cadence, no power, HR elevated (120bpm-ish) and speed is averaging 30kph.
The section between 378.1km and 385.5km has low-ish HR (100bpm), and almost perfect flat power (70W avg), cadence (70 avg) and a 23.4kph average despite not moving from the spot.
44 real laps for 470km (293 miles).
http://www.cyclingweekly.co.uk/news/latest-news/two-riders-clock-323-miles-riding-around-richmond-park-24-hours-234238