I just found this, not sure if it sheds anymore light on the subject....no pun intended
"The Public Order Act , 1986 is not actually about order, but disorder and violent conduct, (something you will probably never see on a naturist beach). Firstly, indecent exposure, an offence I am sure everyone has heard of. In English Law there are two types of indecent exposure and neither of them has any impact on nudity in general. The first is in Statute Law (that made by Parliament), the second in Common Law (a term which describes that which has been accepted over the centuries as being the law).
The basis of the statutory offence is that a male 'exposes his person ('legalese' for penis) with intent to insult a female'. It is a `sexual offence`, that is, there must be a sexual motive to it. For a prosecution to succeed it would be expected that the penis in question should be erect. It cannot be committed by a female although the victim must be of that sex and it must be a deliberate act. The female must also be offended by the behaviour!
It is this law that is used to prosecute the classic dirty raincoated 'flasher'. Don't worry about the much talked about (but rarely seen) 'involuntary erection' problem, this law cannot get you for that. However, it is a relatively serious offence punishable by fine or imprisonment and the police can arrest for it in certain circumstances.
The Common Law offence of indecent exposure is somewhat different This is an indecency offence, not sexual. It can be committed by either sex and no intent is necessary. Unfortunately I don`t know what indecency means - and neither does the Law - so a decision as to what is indecent is usually left to a Magistrate or a Jury. This offence is of a minor nature and could be used to prosecute a 'flasher' where the necessary intent cannot be proved.
The penalty if found guilty is to be 'bound over' to keep the Peace (see later). In practice, this charge will seldom be used, because the effect and penalty of 'conduct likely to cause a breach of the Peace' is the same and that offence does not require proof of indecency.
None of the above should ever have any effect on the practice of naturism.
The most important law effecting naturists it that of 'Breach of the Peace'. This is very old law and anyone taken before a Court will be prosecuted under the Justices of the Peace Act, 1361 - that's not a typing error, it is over 600 years old. It is still used everyday by police officers, no police officer could do his job effectively without it. 'To uphold the Queen`s Peace' is part of the oath taken by a police officer (before a Magistrate) on appointment.
This law affects naturists using traditional beaches in the most important of ways - it actually allows them to be there! I cannot recall this ever being tested in Court but if there was a case to answer it would have been tried sometime in 600 years!
So how does it work? To understand that, you will need to understand what the Peace is. The Queen's (or King's) Peace is the normal state of society and any disturbance of that Peace is a 'Breach of the Peace'. Simple!
The 'normal state of society' varies from place to place and time to time. For example, conduct perfectly acceptable at a football match would not be appreciated in a churchyard. Have you ever seen women at a jumble sale? Imagine that at Harrods, and even here behaviour at the January sales would not be acceptable at any other time. The normal state of society on a recognised naturist beach is nudity - so just by being naked you cannot disturb that state. There is, therefore, no Breach of the Peace and the police cannot stop you from enjoying your day in the sun.
Breach of the Peace is not, technically, an offence, but should you for any reason be taken before a Court for it, you would be bound over to keep the Peace for a given period of time and should you re-offend you would have to forfeit a sum of money. If you refuse to be bound over you could be sent to prison for a period not exceeding 6 months. There is no option of a fine. Most people agree! Don`t worry - as a genuine, responsible naturist this should never affect you.