Looking For The Best Luxury Retail Security in City of London? At Main Security Ltd we understand that we are the first and the last impression for you and your clients/premises and we believe that it is essential for our staff to be very well-kept, knowledgeable, and, fully trained to discharge their roles, therefore all of our security guards are fully vetted, trained, and meet the strict criteria of the Security Industry Authority (SIA). Since 2017, we are leaders in contracting Luxury Retail Security, Residential Security, Corporate Security, VIP Solutions,