Defamation Bill

What would have happened if 22 years ago someone had had a website and they had published their suspicion that the police had had statements altered in regard to a great tragedy such as Hillsborough? Let us suppose that the police had then taken out a defamation action. First, would they have been disqualified from doing so as a public body? Secondly, if an individual police officer took out that action, what defence would have been available to the person who may have been present at the tragedy, and who may have had inside knowledge of what the police statements had contained and how they came out in public?