When does a child become an adult?

David Cameron has suggested reforming the laws on minimum age limits.  In many ways, not before time. It is clearly a nonsense that 17 year olds can own a gun but have to wait to 18 to buy fireworks. But he also says that he would like children who have demonstrated that they are responsible citizens to be allowed to become adults earlier. Uh-oh.  What next?  An adulthood test?  Armies of adulthood assessors?  An Office for Adulthood Entitlement? By all means tidy up the current chaos, but let's not have more bureaucracy to replace it.