UK’s firearm response units have been beefed up in recent years, but Paris atrocities are security forces’ worst nightmare

Britain’s most senior counter-terrorism officials were monitoring events in Paris after the co-ordinated attacks left scores of people across the city dead and injured.

While officially there was no intelligence indicating that the UK was at greater risk of attack, the scale and nature of the atrocities in the French capital are of a kind that British officials have long feared may happen in the UK.

As the severity of the situation became clear, the prime minister, the commissioner of the Metropolitan police and senior security officials at MI5 were being updated. Britain was already on a high state of terrorist alert, with counter-terrorism experts fearing the risk of an attack on the UK is severe.

Already this year, police in London have held an exercise to test how they would respond to marauding gun attacks in the centre of the capital. The last exercise followed the January attacks on the Charlie Hebdo offices.

Britain has already boosted the capacity of its firearms response to terrorist gun attacks following past atrocities around the world – including in Mumbai in 2008, when terrorists staged multiple and co-ordinated gun and bomb attacks across a major city.

Proximity to France will lead UK officials to review border security. But the emerging detail points to the attacks being the nightmare of every western security official: determined, armed attackers, marauding through a city and shaking a major western country to its core.

Scotland Yard has created a special forces-style unit of armed officers to counter the threat of a terrorist gun attack in Britain. The 130 counter-terrorism specialist firearms officers who make up the elite unit have been equipped with new weapons and retrained in new tactics, such as fast-roping from helicopters and storming burning buildings to rescue hostages and shoot or arrest terrorist gun attackers.

They have been issued with SIG 516 weapons and trained to shoot to the head if necessary. Armed officers are traditionally trained to shoot towards the centre of the chest.

The unit has trained alongside the army’s special forces to respond to assaults such as the Mumbai attacks and the 2013 Westgate shopping mall attack in Nairobi, which developed into a siege.

The terrorist atrocity in Paris is of such a scale – the worst in Europe since the 2004 Madrid train station bombings. Assumptions about what atrocities the terrorists can inflict to the tactics and capability needed to respond will, in time, need to be revisited.

Police and community groups in the UK will be bracing themselves for any backlash if it is established those behind the attacks were claiming to act in the name of a particular religion.

The vast majority of Muslims abhor such attacks and regard it as a perversion of Islam. Nonetheless, Muslim groups in Britain say there has been a backlash after the 9/11 attacks in the US, other events overseas and after 7 July 2005 attacks on London and the murder of Lee Rigby in London.

British counterterrorism officials regard their French counterparts as among the best in the world, with tough laws to counter the threat of extremist violence and the elevated threat from Islamic State’s ability to attract Europeans to their cause.

Despite arguably tougher measures than Britain, it was not enough to protect the French capital and its people. Security services across the west were alarmed throughout 2014 by the growth in the potency of Isis, and its ability to attract western youngsters to its cause.

Any hopes that the dangers were merely theoretical or exaggerated were dashed by attacks in Sydney, New York city and Ottawa in late 2014 and then Paris in January 2015, which demonstrated terrorists had the ability and intention to strike the west on its home soil.

Those attacks ranged from an individual seemingly acting alone to a group coordinating their efforts and carrying out an attack involving a degree of sophistication.

The danger from so called leaderless jihad, where jihadi propaganda incites “lone wolves” was added to the threat from more directed and sophisticated plots. In the event of gun attacks in the UK, police would lead the response with the army in reserve.

Police in Britain are traditionally unarmed, but have several kinds of specialist armed units. Roving armed patrols routinely drive around urban areas in Britain but would be reinforced by other police armed units, and then if deemed necessary, by the military, under plans devised by top counter terrorism officials. They are sure to be reviewed after the Paris attacks.