The two person rule in respect of establishing the public element of the offence of outraging public decency contrary to the common law can be satisfied if there were two or more people present who were capable of seeing the nature of the act, even if they did not actually see it. (newlawjournal.co.uk)
Nude (2) For the purposes of this section, a person is nude who is so clad as to offend against public decency or order. (slaw.ca)
It was not enough that the act was lewd, obscene or disgusting and that it might shock people; it had to be of such a character that it outraged minimum standards of public decency as judged by the jury in contemporary society. (newlawjournal.co.uk)