This Act created a legal framework for the exercise of police powers, and provided Codes of Practice to regulate the use of those powers. The Codes, in particular, were once regarded as something of a landmark in civil liberties legislation. With the passage of time, it became clear that the world had changed, and revision was deemed necessary to deal with problems of terrorism, organised crime, firearm offences, drug trafficking, etc. In 2004, new Codes came into being, and while they are all important from the standpoint of "knowing your rights", it is perhaps Code B which is of greatest interest to us, as it deals with police powers to search premises and to seize and retain property found on premises and persons.
The 2005 Serious Organised Crime and Police Act (SOCA) modified nearly all powers of arrest of PACE and introduced the notion of "serious arrestable offences" - a very broad category.
Turning to Warrants, Section 8 of PACE is entitled "Other Police Powers of Entry"; Magistrates may authorise the police to enter and search premises in cases where the police reasonably suspect that a serious arrestable offence has been committed. There must also be reason to believe that it is not practical to gain entry otherwise and that there is material on the premises likely to be of substantial value to the investigation concerned.