25 December isn't exactly a day you'd expect a peak in public transport use. However, figures from UCL's Oliver O'Brien show that Christmas Day 2011 witnessed the greatest number of simultaneous bike hires since the scheme's inception.
The maximum number of bikes simultaneously on the roads during 25 December was 2,065 (from about 5,000 available). By crudely inspecting Oliver's graphs, the average value of this measurement over the past year appears to be just under 1,000 bikes. Figures for the total number of journeys during the day are not available. A good rule of thumb, according to Oliver, is to multiply the number above by 20, indicating around 41,000 hire bike journeys on Christmas Day.
We'd speculate that there are several factors behind the spike. The lack of other public transport options on Christmas Day (except for much more expensive taxis and minicabs) must have played a large part. But the mild weather and quieter roads would also have tempted many onto two wheels for a spot of recreational cycling. Certainly, we enjoyed our own Christmas bike ride through Regents Park and saw many others making use of the scheme.