In many countries all over the world you do not need to be licenced to be a Close Protection Officer but in the UK one has to be licenced through the SIA which is the Security Industry Authority. In order to gain a licence one has to provide personal details and a background check is done in order to see that you have no serious convictions.
This is the main reason why the SIA came about as before this anyone could have worked in the security industry and the stereotypical “Tough-Guys” who had previous convictions often ruined the reputation of the security industry. The SIA has made the security industry professional and it is really important that the standards are maintained.
You can visit the SIA website here