This hasn't happened to me but a situation at work involving the police and a student I teach has prompted me to ask.
If you are questioned by the police what are your rights? Do you have to answer? Can you immediately insist on legal advice?
When should they caution you? When should they arrest you?
The student I taught had an alibi for the crime he was accused of but yet was questioned for over 2 hours in his home. Was this legal?