IIRC...The Yam RD 250 was single handedly responsible for changing British bike laws.

Prior to 1975 ( I think, close enough!)...anyone could ride up to a 250cc M/bike in the UK...
...on a learners permit.
No lessons, no prior experience..just buy it...ride it

Along comes the RD 250...BOOM......250cc's doing what 500cc's used to do!!!

Quick as a flash...learners were restricted to 125 cc....

Jo