You must give your vehicle registration number, your name and address, and that of the vehicle owner (if different) to anyone with reasonable grounds for asking for those details.
If you do not exchange those details at the scene, you must report the accident at a police station or to a police officer as soon as you can and in any case within 24 hours.
Then perhaps you need to know what the term reasonable grounds mean. one man can strike another man in the face but the man who was struck may have paid him to do so. would there be reasonable grounds for arrest?