Fearless Prosecution

Being as his attacker was identified and spoken to at the scene by police, bar manager is keen to see the culprit charged.

How do the police go about this?

Try this:
When he attends the police station, the investigating constable informs him that they are "unable to take a statement in the police station" and makes an appointment to attend his home to take a statement.

The police do not keep the appointment.

Bar manager phones the police the following day, and is informed that police will attend his home at 3pm, to take a statement.

The police do not keep the appointment.

Bar manager attends the police station to try to get things happening, and is informed that police will call at his house "sometime tonight" to take a statement.

Police do not turn up at his house.

He rather emphatically makes his views known at the police station. (Days have now passed). The investigating constable has a chat, using lots of phrases along the lines of "Do you really want to do this?" and "He won't like it if he is charged, are you sure you want to rock the boat in this manner?" and so on & so forth......

Mine Host has a chat with the constable, who obtusely states that she is "unable to comment about an ongoing investigation" and tersely notes that Mine Host is not a complainant in the matter, and thus isn't entitled to know anything!

Oh boy, greenhorn Constables..... So Mine Host has an informal chat with one of the police Sergeants. The Sergeant points out that no complaint has yet been made, thus the police are unable to investigate.

This gives a good starting point to the informal chat. Mine Host makes it plain, (in the course of conversation) that members of the public who cannot even get a complaint heard by the police, let alone have their attacker charged, have considerable resources at their disposal.

The Sergeant doesn't miss this implication. He is aware that a complaint about poor policing, driven by Mine Host, will not only go direct to the correct authorities, but will be very well worded and will likely have maximum effect upon the Constable's career.

Stand by for a sudden reversal of policing policy.