No such thing as a CBT in my day, just got the bike and started riding. The roads were a lot quieter in those days, so we got away with it, of course, the roads are very quiet at the moment so allowing someone to ride without a CBT, especially if they has one and it has run out, may be a good idea. I remember in the 1950's (yes I am that old) we moved to England from France, My dad was French, at that time he could not transfer a French license to an English one, but because of the Suez crisis, learners were allowed to drive on L plates without supervision. Dad took the english driving test and failed for not giving due courtesy and consideration to other road users, well he had been driving in Paris for 20 years, what did they expect?