The law distinguishes between articles which are made or adapted for use for causing injury to the person (which would include the folding baton in the brief case, cited above) and those which are not but which are intended by the person having them for use as such weapons. A baseball bat is not a weapon but having one in a public place when you intend it to be used as a weapon is an offence. It's no defence to show that you have it for self defence,either as a matter of course or on the off chance that you might be attacked . So carrying it or having it in the car or in a pub 'for protection'' is no answer.Public place' includes any highway and any other premises or place to which, at the material time, the public have, or are permitted to have, access, whether on payment or otherwise.
If someone has a baseball bat in the car it may be reasonable to infer that they have it with them for use as a weapon !