I remember a case some years ago where a traffic offence case was dismissed after a defence barrister claimed that the police officer who cautioned his client was not wearing a police cap, which at that time was a required piece of attire. We see from the various TV programmes that this does not seem to be the case nowdays, but does a traffic officer have to be in uniform to act on traffic offences? Eg, can a plain-clothes CID Officer stop a driver for using a mobile phone?