The company was formed by Derek McDonald who was until 2011 employed as Senior Protective Security Advisor, with the Protective Security Advisory Team (PSAT), Security Services Group (SSG), MoD. 

In his former role, Derek headed the Security Services Group Advisory team  for Scotland and NI, advising on appropriate protective security measures and acting as intelligent client for the very Highest Value Military, CNI, Royal Residences, NHS and Nuclear sites throughout the UK. In the course of these duties, liaison with HOSDB, CPNI, Police and other agencies vested with security and counter-terrorism responsibilities was normal. 

D-Four is not affiliated to any suppliers of equipment or installation companies. Our aim is to provide clear, independent, unbiased advice on security threats and counter-measures, based on CAPABILITY. This ensures no colouring of advice for clients. Our advice is based on the standards and approach demanded in JSPs 440 and 480 and recommendations for equipment, where requested, will centre on proven equipment from the SEAP CSE or that proven in current industry use.

D-Four is currently carrying out security consultancy work for NHS Scotland, as well as other large projects. We have completed numerous tasks for security integrators, high net worth clients, architects, businesses and other consultancy companies.

We are security cleared to SC level and are noted for our discretion. we are used to and comfortable in agreeing NDA's for client information and commercial relationships.

Derek McDonald has been a FULL member of the ASC since 2012.