They don’t like to use the ‘Q’ word in counter-terrorism. It’s a bit like blurting out the name of the Scottish Play in a theatre. At Christmas parties, members of the security agencies insisted they had never been busier but once the year had turned and they were no longer tempting fate, they were prepared to admit that 2018 was a bit ‘quieter’. There were, for instance, far fewer arrests for ‘attack planning’, as opposed to downloading or sharing instructional and propaganda material. Last year, there were only four foiled attacks and one unsuccessful vehicle attack on Parliament. Right at the last gasp, with three hours to go to New Year, a knifeman in Manchester stabbed a couple and a police officer, but did not kill anyone.

2017 was a different story. There were attacks on Westminster in March, the Manchester Arena in May, London Bridge and Finsbury Park in June and Parsons Green in September, with a total of 36 deaths and more than 100 injured. Ten other plots were foiled: there was a Taleban bomb-maker carry-ing knives stopped yards from Downing Street; a mother and her two daughters were held after buying a knife and rehearsing an attack in the same area; and a man was arrested in an undercover sting with a fake suicide belt, planning to kill the Prime Minister.

Why was 2017 so violent? For one thing, there was a distinct copycat pattern. Khalid Masood, the ‘lone actor’ who carried out his attacks on Westminster Bridge and just outside the Houses of Parliament, inspired a whole series of others to follow his example. Three of the foiled plots took place in Westminster. In the London Bridge attack, led by Khuram Butt, the method used was identical. Salman Abedi, who launched the suicide bombing against children at Manchester Arena, appears to have inspired Ahmed Hassan to launch the bomb attack on Tube commuters at Parsons Green. Hassan used the same recipe, but fortunately with less effect.

Masood was himself inspired by a series of attacks that had taken place on the Continent, particularly in France and Belgium. These had featured as instructional material in a pro-Isis magazine called Dabiq, produced by western recruits who had joined the group. The magazine was distributed using Facebook and WhatsApp.

In September 2016, Dabiq had to be renamed because the town from which it took its name fell to Turkish-backed militia. The town was said to be where the last great battle between the forces of the infidels and the believers would take place. When Dabiq fell, the magazine was renamed Rumiyah, in reference to the last great battle between the forces of Rome and the believers. Rumiyah ran a series of instructional articles called ‘Just Terror Tactics’, riffing on the ‘just do it’ approach to terrorism. Rumiyah’s last edition came out in September 2017, a few weeks before the fall of Raqqa, the Isis capital in Syria. This debunking of Isis’s prophecy may help explain why 2018 was a quieter, safer year. The grand Islamist prophecies and claims for the caliphate failed to materialise.

One of the significant ‘push factors’ in the Islamist attacks of 2017 was the idea that the world was about to end. When he was still alive, Osama bin Laden propagated the idea there are two camps — the infidels and the believers. You are either on one side or the other. Terrorists are motivated by the need to prove themselves to Allah before the Day of Judgement, lest they spend eternity in Hell. This may sound fanciful to a secular audience but we know from decrypted online conversations between jihadis that this fear is very real. In recent years, extremists continued to promote this apocalyptic vision, using Hollywood-style videos on YouTube to reinforce their point. These videos have titles such as The End of Times and The Punishment of the Grave, and are often accompanied by images of the fall of western civilisation.

Instead we saw the fall of Raqqa, in October 2017. It was the end of Isis as we knew it. A couple of thousand fighters died beneath the rubble, uncelebrated in their ‘martyrdom’. And that, said Donald Trump a year later, was that. Job done, ‘mission accomplished’, time to go home, troops out.

Except that it isn’t the end, and while it’s comforting that 2018 was relatively quiet, there’s a great danger of complacency in 2019. The Isis hardcore, around 2,000 fighters of all nationalities, is holding out around Hajin in eastern Syria. Its publications still circulate online and its videos are on YouTube. The bomb-making video Salman Abedi used turned up in half a dozen investigations in 2018 alone. Isis is still producing new videos and has left an online legacy of instructional and inspirational material, circulating around the internet in perpetuity.

The internet has become a training camp. Travel is no longer necessary and the security services cannot catch you crossing borders. The instructions are straightforward, easy to access and packaged with the glossy graphics of a video game. They appeal to isolated young men in their bedrooms, many of them suicidal, with no life beyond their phones and keyboards. Most of them are Muslims, but not all. In June 2017, Lloyd Gunton, aged 17, used the material he found online to plan an attack on a Justin Bieber gig in Cardiff in the name of Isis. He had not converted to Islam and had no plans to do so. A raid in the same city in August last year  produced a quantity of TATP — the same explosive used by Abedi — in the fridge of two white heroin addicts.

This Christmas, there was no one in counter-terrorism custody for the first time in several years in Britain. However, there were still a number of attacks in December. Five people were killed at a Christmas market in Strasbourg. In Morocco, Isis-affiliated rebels filmed the execution of two female backpackers from Scandinavia. Radicals are ready to take advantage of the death and destruction from the conflict in Yemen and from the instability in countries like Libya, Egypt, Somalia and Pakistan. Individuals are still travelling out to these places and some will return, inspired and instructed.

I would like to believe that the terror threat has receded but that would be foolish. Like all wars, this one will come to an end, but it will be a while yet.