Gah! Of course they didn’t have a warrant! This isn’t a shock, it’s the whole damn point of this farrago of nonsense. In order to obtain a warrant, the police would have had to go before a magistrate and argue why they needed one, and what offence had been committed. I suspect, and clearly the police did too, that magistrates would ask what steps the police had taken to obtain information already, what grounds they had for believing that the suspect would not co-operate and so on. There is not remotely a guarantee that they would have got approval for their request.
So Plan B was needed. And Plan B was to arrest Damian Green on an arrestable offence, thereby triggering section 18 of PACE. The wording is clear:
18. Entry and search after arrest. —
(1) Subject to the following provisions of this section, a constable may enter and search any premises occupied or controlled by a person who is under arrest for an arrestable offence, if he has reasonable grounds for suspecting that there is on the premises evidence, other than items subject to legal privilege, that relates—
(a) to that offence; or
(b) to some other arrestable offence which is connected with or similar to that offence.
Accepting that ‘procuring misconduct in public office’ is an arrestable offence, clearly the police were in the right here. They didn’t need a search warrant to search Green’s home or constituency office. But would the Speaker have been able to demand they produce one before allowing them entry into the Commons? Well, he seems to think so, though I don’t quite know on what basis.