This idea was featured on Radio 4 on monday morning and is also in the telegraph - Nick Freeman (the motorists loophole lawyer) is trying to drum up support for a scheme to force cyclists to register and display a number plate type thing.
I get that there are plenty of selfish and sometimes dangerous cyclists out there, but the numbers of deaths and injuries caused by dangerous cycling is a minuscule fraction of the numbers caused by careless driving and the whole idea seems totally unrealistic to me.
(1) For number plates to work as a reasonably reliable registration method for cars, the manufacture of number plates has to be quite tightly controlled - criminals do clone plates but it's not easy for an ordinary member of the public to get a plate without proof of ownership, and plates are fixed to the correct car and generally stay put. Any kind of wearable registration plate for cyclists would necessarily be something portable and would therefore be so easy to lose or nick that it would be functionally useless as a means of identification because there couldn't be any means to verifiably ensure that each plate was only ever carried by the correctly registered individual associated with that number plate.
(2) cyclists don't come into the world as fully formed MAMILs - and the sight of a 6 year old wobbling along the pavement next to a parent is quite normal. There's no sharp divide between a kid just learning and a fully independent cyclist, no test to pass or license to grant. There's just a gradual build up of skills and road-sense and a gradual reduction in parental supervision. so there's no rational way to define when someone should start being registered (presumably no one thinks it should apply to kids who are just learning)
(3) its frankly stupid to put up any kind of additional barrier to make it more complicated to make a trip by bike rather than getting in the car. It's currently just about a reasonable balance for me for a lot of journeys - a tiny bit of extra hassle to find my helmet and D-lock, but the benefit of not having to find or pay for parking balances that enough that some fraction of the car-miles I might otherwise make, generating traffic congestion and pollution, gets turned into the green alternative of cycling. Upset this balance by making it a legal requirement to wear and carry this proposed registration plate and the net effect will be to drive up car traffic at a time when we should be doing everything we can to achieve the opposite.