There is a difference in the way a suspect for a crime is processed in the UK and the US (also Australia, Canada and New Zealand).

Where in most jurisdictions an arresting officer requires evidence of the commission of a crime before making an arrest and the suspect has to be arraigned in a court as soon as possible. in the UK the arrest is made after the arresting officer only “suspects” the offence has been committed. After the arrest enquiries continue to establish if there is sufficient evidence for a prosecution to proceed. While this investigation continued the suspect may be released on police bail to return to police custody at a future time stated on the bail bond, or to report to police to ensure they do not abscond.

Elsewhere bail is only granted by the court or by police pending the first court date.

The presumption of innocence still exists until convicted in a court

Incidentally, a few decades ago the UK changed their caution upon arrest. While the suspect still has the right to silence and to refrain from making any statement if they do not mention any legal defence at the time of arrest/questioning they may not necessarily rely on this defence in court.

“You do not have to say anything. But, it may harm your defence if you do not mention when questioned something which you later rely on in court. Anything you do say may be given in evidence.”