All police officers in the United Kingdom, whatever their actual rank, are 'constables' in terms of their legal position. This means that a newly appointed constable has the same arrest powers as a Chief Constable or Commissioner. However, certain higher ranks have additional powers to authorize certain aspects of police operations, such as a power to authorize a search of a suspect's house (section 18 PACE in England and Wales) by an officer of the rank of Inspector, or the power to authorize a suspect's detention beyond 24 hours by a Superintendent.
What can't only Superintendent-ranked UK officers do?