Yes, quite right Eddie.
But I have known prosecutions under these acts to be launched when (say) a train where 90% of its passengers were travelling to a match (and the prosecution can show that this was so). The spirit of the Act is to prevent trouble occurring in connection with sporting events. (This particular Act relates to all sporting events. There is another Act with more provisions relevant specifically to football).
If a prosecution is launched as I outlined above there will undoubtedly be a legal argument between the defence and the prosecution as to whether the law applies or not. This will be heard by the Magistrates (these offences are “summary” offences, which means they can only be heard by Magistrates). In making their decision the Bench will refer (or more specifically be referred by both sides) to precedent case law, usually set by higher courts, to help them decide.
The problem with many laws such as this is the interpretation to be placed on the phrase “principle purpose” as it is not defined in the Act. It could be argued that because the vast majority of the passengers are travelling to the match, then that is the vehicle’s Principle purpose. Equally, it could be argued that when the vehicle was originally scheduled to run the match may not have even been scheduled to take place. So how could its principle purpose be to transport people to the match?
It makes for a fascinating argument (and nice fat fees for m’Learned Friends!)