"The 33 bhp category disappears in the EU from January as more age related restrictions come in, but there will now be a 47 bhp intermediate licence category."
The Harley 883cc Sportster and the 400cc Ninja have about 45 peak horsepower- maybe the UK rule makers looked at these 2 bikes.
My Honda 600cc cruiser has about 33 peak horsepower with a custom exhaust and rejetting, giving it about the same top speed as a 250cc Ninja, but it is slower in corners because it weighs more and scrapes the footpegs sooner, with its lower seat and frame.
“It is difficult to get a man to understand something, when his salary depends on his not understanding it.”
― by Upton Sinclair, who helped clean up the meat packing industry and other factories