what power did alex dowsett put out during his hour record?
We cannot know exactly unless Dowsett's team releases it, but we can make a reasonable estimate. The most important unknown is Dowsett's drag area, or CdA, so below I have calculated the power needed to average 52.937 km/h for various values of CdA, given the assumptions noted on the figure. Notably, rho is air density in the velodrome and a trackside observer provided the estimate of 1.16 kg/m^3; Dowsett is listed as 75 kg for his "official" weight so 85 kg is an estimate of the rider plus bike plus shoes plus helmet plus suit; eta is drive train efficiency and for fixed gear bikes with a good chainline losses tend to be around 2.5%; and the coefficient of rolling resistance for track tires on a smooth wooden velodrome surface will be in the range of .0025 to .003. Thus, if Dowsett's drag area were around 0.195 m^2, his average power would have had to have been about 400 watts.