I understand you are from Hong Kong, so you may know this guy Mayank Vaid who did the fastest ever time for this out of order triathlon the "Enduroman": Run from London to Dover 140km, swim across the channel, bike 290km to Paris. Took him 50 hrs 24 min, which was the world record as of last Sept, so a "bit longer" than the Eurostar:

https://www.hindustantimes.com/...fCAL1xq5NkustdO.html

He probably would have smoked Mark Cavendish on the sprint finish on the bike in Paris had Cav done all legs too