This guy was hard work for me.

[flecc]

I think he is just a strong young lad and he is in top gear.

Yes, just a fit young man, I could and did do the same even in my 60s before adopting e-power for the first time at 67 to help with heavy trailer pulling. These days there are very large numbers of London cycle commuters keeping up 20 mph during long commutes, and they aren't all very young.

Have a look at that video above at 2m 30 for a few seconds to see him lean forward and put in an extra burst of hard effort to regain speed. It shows he's strong.
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[anotherkiwi]

Just got back from a test ride on Number Two and I am still good for 30-32 km/h on the flat (cut off speed 25 km/h). That was at 46:13 and the bike wasn't loaded at all, just the chain, my wallet and a safety vest in the pannier. Downhill 46:11 and lying down I pushed to over 60 km/h just about spinning out, sitting up in a more dignified position I managed to pedal to 51.7 km/h down the longer 3.8 km hill. Taking things easy 44 km/h is the number most seen on the speedo going down and 18-23 km/h going up.

More details, and photos, on the evolution of Number Two to come in the build thread tomorrow.