Risk is surely proportional to how many people you come within 2 metres of. If you are going out self-supported (ie. leave home with all the food/water you need for the ride) going out for a 10 hour ride likely poses less risk than nipping back to the supermarket to pick up the coffee you forgot.
Do you not think risk is proportional to ride duration? Or do you really think a 10 minute jaunt is just as risky as a 10 hour ride?
Can you really read the list of restrictions on the BBC website and decide that a 10 hour solo bike ride is justifiable?