Declining name and birthdate when answering police questions until grounds for suspicion has been precluded or reasonably established

Question

Alice is approached by police following complaints that a woman wearing a yellow jumper has committed some minor offence or another.

Sometimes, in such scenarios police will meticulously investigate the facts of the situation before bothering with ascertaining even so much as her name.

Other times they will firstly ask for her details to check her history before proceeding with their inquiries as to the situation which gave rise to their encounter with her, and if she satisfies them that no offence has been committed by the woman in the yellow jumper, then they will just as happily leave her alone and be on their way without being concerned about her identity.

In the former types of encounters, as they have received complaints not not independently established any reasonable likelihood that she had committed an offence, is Alice entitled to decline her details while pointing out the grounds of her refusal while indulging their questions as to her acts in question as being simply of the yet-nameless woman in the yellow jumper?

Or is a mere yet-unsubstantiated complaint at that preliminary stage of investigation grounds enough for reasonable suspicion of an offence?

Both legally and in typical practice, is Alice not quite reasonably entitled to insist that they carry out the rest of their inquiries without ascertaining her name?

Even more fundamentally than this, perhaps Alice while perfectly confident of her innocence is late for an appoint and in a rush to go somewhere as it is. In this case, is it not then both legally and practically quite reasonable at this stage for her to decline to cooperate with their questioning, whether nameless or identified? One would imagine that the answer to this aspect of the question would hinge on whether or not she is being detained (or if she is not being detained then whether they would at this stage have any grounds to detain her, ie whether she should have any fear of being lawfully detained on the mere basis of a member of the public's so far entirely unsubstantiated/uncorroborated allegations.)

What is the standard of suspicion/probability that is required then of the police to be able to detain Alice, and is she obligated to assist in their efforts to establish this level of probable suspicion if it isn't already established?

Answer 1

I am not sure what the standard is, under UK law, for the police to be able to lawfully insist on basic identity information, or to briefly detain Alice. (In the US it is "Reasonable suspicion" or "founded suspicion".)

But since Alice apparently matches a very superficial description of a person who has been reported as engaging in criminal activity, it is plausible that the police will ask for her name and contact info, and will make some effort to insist if she initially declines.

It may well be tht the police do not have sufficient grounds to lawfully compel Alice to respond. But if Alice has an appointment and wishes to be on her way as promptly as possible, it may well be that her best choice is to answer the oficer briefly and politely. If she refuses, this may well result in the officer arguing with her as to whether she can lawfully refuse. It might even lead to an attempt by the officer to detain here while inquiries proceed. Such detention might well be unlawful, but resolving that issue might well take significantly longer than responding to the questions.

To be clear, I am not advising anyone to waive his or her rights. I am merely commenting on the probable practical effect of insisting on them. I will be very interested to read an answer making clear what the UK legal standard is in such a case.