Yes the City of London is also referred to as "the square mile" - a self explanatory title.

Also worth noting they broke up all other forms of transport i.e cars, buses, vans, etc. So it's more like cyclists make up 25% of road traffic against powered vehicles in a very small area of London, at particular times of day.

I do 40+ miles a day on road across London and would be really surprised if these figures hold up in general.