Pass your test on a 125cc motorbike and you are entitled to a full licence that is restricted for two years to motorcycles with a moderate power output (25kW or 33bhp). After two years this restriction is automatically lifted and you will be allowed to ride a bike of any size.

Note that the restriction is one of power, not capacity. Any larger motorcycle can be restricted to 25kW, indeed many middleweight bikes like 500s and 600s are readily available from the manufacturers with a restrictor that can be removed after your two years. Or choose a smaller bike - Kawasaki claim 24kW for their Ninja 250R.

If you are over 21, or reach 21 before the end of the two-year period, you can take the test again on a big bike if you can't wait that long. This is known as Accelerated Access and the same rules apply as for Direct Access