Immunity from suit
No person taking part in legal proceedings, such as the judge, the advocates including the barristers and solicitors representing their clients, the witnesses and the parties themselves can be sued for anything written or spoken in the course of the proceedings.
The immunity from suit is absolute and cannot be defeated by malice
In Taylor -v- Serious Fraud Office  2 AC 177, 207F Lord Hoffmann stated:
“The policy of the immunity is to enable people to speak freely without fear of being sued, whether successfully or not. If this object is to be achieved, the person in question must know at the time he speaks whether or not the immunity will attach. If it depends upon the contingencies of whether he will be called as a witness, the value of the immunity is destroyed. At the time of the investigation it is often unclear whether any crime has been committed at all. Persons assisting the police with their inquiries may not be able to give any admissible evidence; for example, their information may be hearsay, but nonetheless valuable for the purposes of the investigation. But the proper administration of justice requires that such people should have the same inducement to speak freely as those whose information subsequently forms the basis of evidence at a trial.”
The immunity will extend to statements made by the witness to a party and his legal advisers with a view to giving evidence.
It applies to out of court statements which are part of the process of investigating a crime or a possible crime with a view to prosecution.
It will apply to the initial report of a crime to the police as to a matter which might lead to a prosecution, and therefore to cover the initial report.
The only exception is the tort of malicious prosecution.
In Roy v. Prior  A.C. 470.
“The immunity does not apply to actions for malicious prosecution where the cause of action consists in abusing legal process by maliciously and without reasonable cause setting the law in motion against the plaintiff. It does not matter that an essential step in setting the law in motion was a statement made by the defendant to a prosecuting authority or even the court.”