If you want a stable and well-paid job in London, security is a smart choice. After you complete your SIA Door Supervisor training in London, many career paths open for you. The security industry in London is evolving fast. From nightclubs and offices to big stadiums and shopping centres, trained security staff are always in demand. To work legally, you must have a licence from the Security Industry Authority (SIA). Once you get your SIA badge, you can start applying for exci