The SIA, which stands for the Security Industry Authority, is the governing body which regulates the private security industry. It does this through two ways; the licensing which controls various areas of the industry’s licensing, and the voluntary scheme that it manages.
Becoming a member of the Approved Contractor Scheme (the voluntary scheme) gives you a certificate which indicates the high quality of services that your business can provide. It isn’t fool proof, as you can still pass tests with only a superficial understanding.
For those looking for a top quality private security firm to outsource their security requirements with, a good choice is to look for a business which is SIA approved. This will give you a smaller list of options, but you will be sure that the services which are offered will be effective, and probably that they’ll be worth the costs associated with the services as well.