What does a person of reasonable firmness mean under English Public Order Act?

The term "person of reasonable firmness" is used in the Public Order Act 1986 to describe the hypothetical person whose perception of the conduct of a group of people is used to determine whether a riot or other public order offence has been committed. The term refers to an ordinary person who is not particularly courageous or nervous, but is of average sensitivity and resolution. The legal test for whether a riot has occurred requires that the conduct of the group taken as a whole is such as would cause a person of reasonable firmness present at the scene to fear for their personal safety. In other words, it is not necessary for a member of the public to actually be in fear for the offence of riot to be committed. Rather, the test is an objective one, based on the conduct of the group as a whole, and the likely effect of that conduct on a hypothetical person of reasonable firmness. The concept of a person of reasonable firmness is used in a number of other areas of English law, such as in the law of self-defence and in the law of negligence. It is a useful legal fiction that allows courts to determine whether a particular set of circumstances would be likely to cause fear or harm to an ordinary member of the public, rather than requiring evidence of actual harm or fear.