Britain’s open borders is a disaster waiting to happen.
With Iran increasingly desperate to strike back against the West, one of the most effective weapons at Tehran’s disposal would be activating sleeper agents already embedded across Europe. The UK is particularly exposed. Since 2018, more than 25,000 Iranian nationals have arrived via small boats across the Channel. Among them will inevitably be individuals acting on behalf of the Iranian state.
The late Iranian Supreme Leader, Ali Khamenei, warned that countries targeting Iran or its proxies would be held responsible. Tehran has already demonstrated its willingness to treat Britain as an adversary, including through attacks on British forces stationed in Cyprus. With porous borders and a growing flow of migrants from hostile states, the uncomfortable reality is that hostile actors may already be inside the country waiting for the moment to strike.
Recent events underline just how real this threat has become.
Last week, four men – including one Iranian national and three dual British-Iranian nationals – were arrested as part of a counter-terrorism investigation into suspected activity on behalf of a foreign intelligence service. According to the Metropolitan Police, the case involves the alleged surveillance of locations and individuals connected to Jewish communities in London. The arrests, carried out across Barnet, Watford and Harrow, come as part of a long-running investigation into Iranian-linked malign activity in the UK.
These arrests are far from an isolated incident. In May last year, four Iranians were detained over a suspected assassination plot on British soil. In September 2025, three Iranian nationals in London were charged with spying for Tehran’s regime. That same month, MI5 revealed it had disrupted at least 10 Iranian-backed plots in the UK since 2022.
The good news is that Britain’s security services are disrupting Iranian activity before it turns deadly. The bad news is how often they are having to do it.
With Britain’s security services already stretched monitoring thousands of individuals on terrorism watchlists, the margin for error is dangerously thin. It only takes one plot slipping through for lives to be lost.
Nor is the threat limited to Britain. In the United States, authorities believe around 700 Iranian “Special Interest Aliens” entered the country illegally in recent years – a designation used for individuals from states considered potential national security threats. Iran’s long record as the world’s leading state sponsor of terrorism means it possesses both the networks and the experience needed to coordinate attacks far beyond its borders.
Even where the regime does not directly order violence, its ideology can inspire others to act. In Austin, Texas, a gunman wearing an Iranian flag shirt killed three people and injured fourteen in a shooting rampage. Meanwhile, UK-based groups have already begun calling for “action” following the death of Iran’s Supreme Leader – language that is deliberately vague but deeply concerning.
Last week, Shabana Mahmood spoke about restoring public confidence in Britain’s justice system and ensuring the state has the ability to enforce the law. That principle must apply equally to national security. A country that cannot control who enters its borders inevitably increases the burden on its security services. Britain’s intelligence agencies may be doing remarkable work disrupting Iranian-linked plots, but they should not be forced to fight the consequences of policy failures elsewhere in the system.
MI5 may be stopping Iranian plots, but they should not have to compensate for a border system that lets hostile actors slip through in the first place.
Make no mistake: the Iranian regime may be under pressure from American and Israeli military strikes, but Tehran’s reach remains global. A cornered regime is often a dangerous one. Its recent missile attacks on Dubai and other targets demonstrate that it’s willingness to lash out indiscriminately.
The regime in Tehran may be entering its final chapter. But history shows that failing dictatorships rarely go quietly.
If Britain fails to take the threat seriously – by tightening border controls, strengthening counter-intelligence efforts and recognising the scale of Iranian infiltration – it risks discovering too late that the enemy was already inside the gate.
