I will attempt to clarify the helmet wearing rule for Retrobike organised rides if I may.
1) Each year Retrobike pays to be affiliated as a club with both British Cycling and the Cyclist's Touring Club. BC and the CTC both provide third party liability insurance. This means that there is some legal cover provided for Retrobike and it's official ride organisers should an accident or incident occur on a ride which leads to litigation.
Basically if somebody were to try and sue for damages, then the entity which is Retrobike has some legal protection.
This doesn't mean that the cover extends to individuals on a ride though, as in you can't have an accident and then claim compensation or protection as an individual using the RB policy.
Essentially the insurance protects Retrobike from everyone on the ride.
In order to validate the policy we have to have some control measures in place which demonstrate that we are fulfilling a duty of care to anyone participating. This includes experienced ride leaders, a well planned route, contingency planning and a full written risk assessment.
The last of these relates to the helmet rule. Anyone who writes a risk assessment will know that there are many tangible risk control measures and many more less tangible risk control measures that can be employed to reduce risk. Perhaps the most tangible and widely accepted control measure, in this context, is the obligatory wearing of a suitable helmet on rides.
In fact it would be inconceivable nowadays not to include wearing a helmet as a risk control measure on a risk assessment.
That is why the rule exists on official Retrobike rides.
Anything else would invalidate the insurance policy.
2) As a ride organiser, and as someone who is very much an advocate of personal choice, I only really get drawn into the 'helmet debate' when it is in the context of organised rides.
Along with the question of insurance above, I also have reasons why I insist that everyone wears a helmet when myself or somebody else has taken the time to organise a ride, and therefore bears some burden of responsibility for what happens during it.
I am realistic about the level of protection a helmet can provide. There are times when they are wholly ineffective, and there may be times when they can make injuries, especially spinal injuries, worse. However, most of the time when the head hits the ground in a crash they can mean the difference between a slightly sore head and a ride ending injury.
I have witnessed many times incidents where a helmet has prevented serious injury. I've also had to call ambulances for people who have chosen not to wear a helmet and suffered otherwise avoidable injuries when they have crashed.
There are few things worse than dealing with serious injuries when out riding. It does often bring out the best in people and can be a very effective team building exercise, the group will always look after the individual no matter how foolish they have been.
But it can also be very traumatic for everyone involved.
So point two is actually rather selfish, in that I'd rather not have a ride I'd organised defined by a traumatic situation and an otherwise avoidable injury.
Likewise it should be reasonable to expect and respect that most ride organisers will probably take a similar position.
So in summary, if you are coming on a Retrobike organised ride, you will have to wear a proper cycling helmet that meets or exceeds current safety testing certification.
If you are out riding elsewhere then the choice is yours and I sincerely hope that it always will be.