Australia, Britain and France have been hit by terrorists previously known to the authorities. Are the security services letting us down, or do we have unrealistic expectations of what they can do?
It quickly emerged after Wednesday’s Charlie Hebdo shootings that the prime suspects, brothers Cherif and Said Kouachi, had a long history of involvement in extremist circles.
The men are thought to have carried out the killings of 12 people in Paris. Both are thought to have died after a hostage siege in the town of Dammartin-en-Goele in northern France.
Cherif was arrested in 2005 while preparing to travel to Iraq to fight for an Islamist cell. He served 18 months of a three-year sentence.
Reuters has quoted US and European sources as saying that Said trained with al-Qaeda in the Arabian Peninsula in Yemen in 2011.
US government sources said both were listed in two American security databases including a “no fly” list.
Both men are also understood to have been on a a British watch and no-fly list, preventing them from entering the UK or passing through a British airport.
France’s intelligence agencies are now likely to face the same questions asked of their UK counterparts after it emerged that the men who murdered Fusilier Lee Riby in Woolwich in 2013, Michael Adebolajo and Michael Adebowale, had featured in seven intelligence investigations.
In Australia the government has ordered an inquiry into Man Haron Monis, who died following a hostage siege in a Sydney cafe last month, after it emerged he had dropped off security watch lists.
Andrew Parker, the director general of MI5, said in a speech yesterday that the UK authorities have stopped three deadly terror plots in recent months, with terror-related arrests up 35 per cent compared with four years ago.
He said: “Although we and our partners try our utmost we know that we cannot hope to stop everything.”
Drawing on the security services’ experience combatting republican terrorists in Northern Ireland, he added: “It’s unrealistic to expect every attack plan to be stopped, even where the perpetrators may in some cases have been on our radar for many years.”
The current level of threat to the UK, he said, is “complex to combat and unlikely to abate significantly for some time”.
Mr Parker said Britain still faces a threat from groups trying to carry out complex al-Qaeda style “spectaculars” that cause mass casualties.
But recent attacks in Australia and Canada are part of a growing number of “crude but potentially deadly plots” too, often the work of volatile “lone wolf” individuals who may work alone and act spontaneously rather than as part of sophisticated networks.
He added: “Such attacks are inherently harder for intelligence agencies to detect.”
Dr David Lowe, an academic at Liverpool John Moores University and former Special Branch counter-terrorism, officer, said terror groups’ tactics have evolved in recent years, with the current trend of two- or three-man teams carrying out attacks echoed the “small cell” tactics adopted by the Provisional IRA in the mid-1970s.
The republicans organised themselves into small independent units which proved difficult for the British security services to infiltrate compared to bigger, more complex groups.
He said: “How the provisionals’ England department operated is a textbook for terrorist operations. It is so difficult to penetrate.”
But he added that following the attacks on New York, Madrid and London in the 2000s, “there is far closer co-operation between the agencies in one state and far greater co-operation between states”.
Nevertheless, counter-terror teams always feel thinly stretched, he said.
“The volume of intelligence that comes in is massive and it has got to be analysed, and analysed effectively. Then you have got the risk assessment.”
Officers are constantly under pressure to justify why they have targets under surveillance if there does not appear to be an immediate risk.
“Of course there is cost. There is only a finite budget at the end of the day.”
He added: “It’s so easy for one to slip through the net. I couldn’t give any reassurance at all that this could never happen in Britain. I think it could.”
Intelligence experts say the authorities in several countries are facing a similar dilemma – how do you keep tabs on large numbers of individuals who may be on the fringes of extremist groups for many years but never break the law?
Raffaello Pantucci, director of international security studies at the Royal United Services Institute, calls them “persistent radical individuals”, people like Lee Rigby’s killers who “sort of bump along in security services’ radars and are of concern for long periods of time, but never seem to cross that threshold of moving into action”.