omic terms is the premeditated use or threat to use violence by individuals or subnational groups to obtain a political or social objective through the intimidation of a large audience beyond that of the immediate victim. Recently the UK is suffering from increased terrorist threats. Terrorist threats are escalating due to the change in nature particularly cyber terrorism is becoming more common. In addition, threats are now more diverse than before – coming from a wider geographical area. This leads to terrorism increasing in severity and increasing casualty risk therefore becoming a security problem for the UK. The unpredictable nature of terrorism further intensifies the threat for the UK.

Terrorist leaders and supporters will carry out a cost-benefit analysis in order to determine whether to carry out a terrorist attack. As a result, to improve the UK’s security policy counter measures need to be in place which will influence these costs and benefits for terrorists. These security measures can be categorised as defensive or pro-active measures. Proactive measures attack the terrorist, their resources and supporters. By contrast defensive measures involve erecting a protective barrier around potential targets.

Arguably, one approach to enhance security against terrorism is deterrence theory. Deterrence models assume individuals so in this case, the terrorist are rational, self-interested actors who aim to maximise benefits whilst minimising costs. Counter terrorism to protect the UK against attacks requires increasing the difficulty for terrorists to strike as well as increasing the risk of failure. For example, installing surveillance technology to deter terrorist activity. Additionally, suicide bombers can be deterred by aggressive state action therefore reducing the threat. However, deterrence relies on the ability to convince potential adversaries that acts of aggression will result in greater costs than benefits. As a result, the effectiveness of deterrence can be questioned. Counter terrorism can result in greater issues as instead of reducing terrorist activity can cause a displacement towards “cheaper” means of terrorism. This may be to other venues or countries where targets are relatively softer. Many studies highlight strong empirical evidence for this substitution effect. Enders and Sandler empirically analyse the effects of some protective measures. They show that metal detectors and body searches introduced at airports have proven effective so far in decreasing sky threats such as hij