What did I see?

[moon]

I've just returned from my commute home during which I saw a guy and a girl on what looked like a normal mountain bike, but it had a large disc of a motor on the front wheel (much larger than a wisper motor) the guy was using throttle only and overtaking the commuters on racing bikes with the girl sitting on the back.

Does anyone know what this bike cold have been?

 

[flecc]

There are several large diameter high powered direct drive motors on the market, makes such as Crystalyte and Puma, and some fit them to existing bikes regardless of their illegality.

These are often 1000 Watts or more.
.