It's written somewhat in jargon but the CPS gives guidance in the section Entrapment on https://www.cps.gov.uk/legal-guidance/abuse-process https://www.cps.gov.

It's written somewhat in jargon but the CPS gives guidance in the section Entrapment on https://www.cps.gov.uk/legal-guidance/abuse-process https://www.cps.gov.uk/legal-guidance/abuse-process. It's relatively readable, it's probably enough to note that a "stay" means that a trial will not proceed (at all). A quote from that section: "Police conduct which brings about state-created crime is unacceptable and improper, and to prosecute in such circumstances would be an affront to the public conscience. However, if the accused already had the intent to commit a crime of the same or a similar kind, and the police did no more than give him the opportunity to fulfil his existing intent, that is unobjectionable."