Lest anyone conclude that rumours of professional racing cyclists benefitting from mechanical assistance during races are no more than wild speculation, here’s a video posted on YouTube that not only explains how it can be done but goes to some lengths to demonstrate that Swiss colossus Fabian Cancellara must have used such a system to win both Paris-Roubaix and the Tour of Flanders earlier this year.

The obvious response is that it is hard to see how “Spartacus” could have gone as fast as he did without a motor hidden inside his bike… Flippancy aside, this is a serious accusation that, as Quick Step manager Patrick Lefevere said, would be “worse than doping; even pure theft.”

The machinery itself is pretty straightforward and indeed already in use in some power-assist cycles. It comprises an electic motor slender enough to slide inside the seat tube with, on the drive shaft, a bevel gear of the type seen in car differential transmissions. A matching bevel gear is fitted to the bottom bracket axle – in this case Shimano Hollowtech II although any design with external bearings would surely do.

The motor is precision-mounted in the seat tube and located using two 4mm screws. It is turned on using a push button and several modes of operation are available. The Gruber system is rated at 200W and will give between 40 and 90 minutes of assistance. Weight is around 900g for the motor and 1kg for the standard battery, although a mechanical doping installation would surely require a (smaller and lighter) custom battery located inside the downtube.

So, 200W of extra power just when it is needed and lasting long enough to get a rider the final 30km or so? For sure, Cancallara’s explosive acceleration from the Boonen group in Paris-Roubaix and his stunning charge up the Mur de Grammont in Flanders had all the hallmarks of such a scenario – except one. A big one.

These things make a loud whining noise. And none of his opponents, who would surely have been alerted by such a noise, appear to have heard it. Nor did any of the spectators on the Mur. Maybe carbon-fibre is as good at muffling sound vibrations as those coming from the road surface.