David Johnston’s journey into the world of crime fighting and national security began far from the corridors of power. Raised in Glasgow in a working class family, Johnston joined the British Army at just 15 years old. At the time, it was possible to enter what was known as “boy service,” a training pathway that prepared young recruits for full military careers.
After learning his craft as an electrical and combat engineer with the Royal Engineers, Johnston volunteered for special service training. He completed the All Arms Commando Course, earning the coveted green beret and joining 3 Commando Brigade.
For a young soldier in the 1970s, the experience was intense and formative. Johnston was deployed to Northern Ireland during one of the most volatile periods of The Troubles. Areas such as Crossmaglen and Forkhill were often referred to as “bandit country,” reflecting the constant threat of violence.
At just 18 years old, Johnston describes feeling almost invincible, like many young soldiers thrown into dangerous environments. The reality was that he was operating in one of the most complex security situations the UK had faced in modern times.
After seven years in the military, Johnston began to think about a different future. Married and looking for stability, he decided to follow his brother’s advice and join the police.
Entering the Police Force
Johnston joined Avon and Somerset Police in the late 1970s, moving from military life into civilian law enforcement. His background as a soldier gave him an advantage in discipline and resilience, but policing presented an entirely different set of challenges.
Early in his career, he moved into the Criminal Investigation Department, commonly known as CID. Over the next 14 years he built a reputation as a dedicated detective, dealing with robberies, violent crime and complex investigations.
During the 1980s and 1990s, policing was undergoing significant change. Professional standards were rising and officers increasingly needed formal qualifications to progress into senior roles.
Recognising this, Johnston returned to education in his late twenties. He completed A Levels and later went on to earn a master’s degree. This combination of frontline experience and academic understanding helped shape his future leadership roles.
Eventually Johnston rose through the ranks to become head of CID in Avon and Somerset as a Detective Chief Superintendent.
For someone who began his career chasing suspects on the streets, running entire investigative departments was a remarkable step.
Leading Homicide Investigations at Scotland Yard
Johnston’s career eventually took him to Scotland Yard, where he served as a commander responsible for homicide investigations.
Murder investigations in the UK follow a structured methodology, guided by a detailed framework known as the murder investigation manual. These processes are designed to ensure every case is handled systematically, from the initial crime scene to the final prosecution.
One of the most important concepts in murder investigations is what detectives call the “golden hours.” The first 24 to 48 hours after a homicide are critical. Witnesses are easier to locate, forensic evidence is fresher and investigative leads are clearer.
Johnston explains that British policing developed a model where large teams could be rapidly deployed to major incidents. These major incident teams included detectives, analysts and specialists who worked together to solve crimes quickly.
This approach helped the UK achieve some of the highest homicide detection rates in the world. At one stage, detection rates for murder in Britain were reported to be as high as 94 percent.
But not all cases are straightforward.
Investigations involving missing persons or cases where no body is found can be extremely difficult. These “no body” murders require detectives to build cases based on motive, circumstantial evidence and investigative intelligence rather than forensic confirmation.
The Reality of Violent Crime
Despite the perception that most murders are complex criminal conspiracies, Johnston says the majority of homicides follow a very different pattern.
Most murders are committed by someone who knows the victim. Domestic violence, arguments and spontaneous acts of violence account for a large proportion of cases.
He also highlights the impact of knife crime, particularly among young people in urban areas. Many individuals carry knives for protection, but the presence of a weapon dramatically increases the likelihood of fatal outcomes.
Often the intention is not to kill, but to intimidate or injure. However, striking an artery or delivering a poorly aimed blow can quickly turn a fight into a homicide.
Johnston believes prevention is key. Addressing issues such as education, mental health support and family stability could significantly reduce violence in the long term.
Hostage Negotiation and Crisis Response
Another fascinating part of Johnston’s career was his work as a hostage negotiator.
Hostage negotiation requires a completely different mindset from traditional policing. Instead of taking control of a situation, negotiators must build rapport with individuals who hold the power.
In many cases, the people involved are not hardened criminals but individuals experiencing severe emotional or mental distress.
Negotiators are trained to listen carefully, establish trust and buy time. Time allows commanders to develop strategies, whether that means a peaceful resolution or a tactical intervention.
Although hostage situations involving terrorists or kidnappers capture public attention, Johnston says most call outs involve suicide interventions.
Police negotiators frequently respond to situations where people are threatening to jump from buildings, bridges or cliffs. Their job is to talk individuals down and guide them toward safety.
It is demanding work that requires empathy, patience and psychological understanding.
Working with Intelligence Agencies and GCHQ
After three decades in policing, Johnston moved into the intelligence world, working with GCHQ.
His role involved helping law enforcement and intelligence agencies adapt to the rapidly changing world of technology. Communications were becoming encrypted and criminals were moving their operations online.
Platforms such as WhatsApp, Telegram and Signal made traditional telephone interception far more difficult.
Johnston worked on technical solutions and legislative frameworks designed to allow investigators to continue tackling serious crime while respecting legal safeguards.
In the UK, intercepting communications requires a warrant signed by a Secretary of State. The system is designed to balance public safety with privacy rights.
He emphasises that intelligence gathering is not about monitoring ordinary citizens. The legal thresholds are high and warrants are typically used only for national security threats or serious organised crime.
Cybercrime and the Rise of Digital Scams
One of the fastest growing areas of crime today is cyber fraud.
Johnston warns that criminals are increasingly sophisticated, using artificial intelligence, deepfake voices and cloned websites to trick victims.
Common scams include impersonating banks, investment firms or even family members. Victims are persuaded to transfer money or click malicious links that install ransomware.
The best defence is caution. Johnston advises people never to click on links sent in unsolicited emails or messages. Instead, they should independently search for the organisation’s official website and contact them directly.
Criminals rely on urgency and trust to manipulate victims. Taking a moment to verify information can prevent devastating financial losses.
A Career in Public Service
Looking back, Johnston describes his 30 years in policing and his later work in intelligence as a privilege.
He received the Queen’s Police Medal for his service, an honour presented at Buckingham Palace by the then Prince Charles.
Despite the recognition, he insists the award reflected the work of thousands of officers who served alongside him.
From soldiers on the streets of Northern Ireland to detectives solving murders and negotiators saving lives, Johnston’s career provides a rare insight into the realities of law enforcement.
His message is clear. Behind every headline about crime or national security are teams of dedicated professionals working quietly to keep the public safe.
