At age 21 you can

Adoption
You can adopt a child.

Legal
If you were ‘looked after’ by the local authority between ages of 16 and 18, the local authority continues to be under a duty to advise and ‘befriend’ you, and in exceptional circumstances, to assist you financially up to the age of 24.

Political participation
You can become a Member of Parliament, a local councillor or a local mayor.

This is not a comprehensive list but a range of things we think you may find useful.

Need proof of age? We suggest the CitizenCard.