Jeremy Corbyn is correct in saying that there is a strong connection between the terrorist threat in Britain and the wars Britain has fought abroad, notably in Iraq and Libya. The fact that these wars motivate and strengthen terrorist organisations like al-Qaeda and Isis has long been obvious to British intelligence officers, though strenuously denied by governments.

The real views of British intelligence agencies on the likely impact of Britain taking part in wars in the Middle East are revealed in a Joint Intelligence Committee (JIC) assessment dated 10 February 2003, just before the start of the invasion of Iraq led by American and British forces. It is marked “top secret”, but was declassified for use by the Chilcot Inquiry and, though it was referred to by several publications, attracted little attention at the time.

It says, “the threat from al-Qaeda will increase at the onset of any military action against Iraq. They will target Coalition forces and other Western interests ina the Middle East. Attacks against Western interests elsewhere are also likely, especially in the US and UK, for maximum impact. The worldwide threat from other Islamist groups and individuals will increase significantly.”

Jeremy Corbyn highlights link between foreign wars and 'terrorism at home'

An earlier JIC assessment dated 10 October 2002, also declassified by Chilcot, says: “Al-Qaeda and associated groups will continue to represent by far the greatest terrorist threat to Western interests and that threat will be heightened by military action against Iraq.”

Corbyn is saying almost exactly the same today as the JIC predicted in 2003. He cites with approval experts pointing to “the connections between wars our government has supported or fought in other countries and terrorism here at home". He adds that their assessment in no way reduces the guilt of those who attack our children, but that an informed understanding is essential in order to fight rather than fuel terrorism.

The JIC conviction about the benefits to al-Qaeda of the Iraq war was swiftly borne out after the invasion as it expanded from being a small group of militants, perhaps less than a 1,000-strong based mainly in the mountains of southern Afghanistan and north-west Pakistan, into a global movement. Al-Qaeda in Iraq, taking advantage of the destruction of the Iraqi state, developed into one of the most powerful and influential terrorist movements in history, and later transmuted in Iraq and Syria into Isis.

Corbyn says that “we must be brave enough to admit ‘the war on terror’ is simply not working”, adding that “we need a smarter way to reduce the threat from countries that nurture terrorists and generate terrorism.” Again, this is demonstrably true as vast resources have been poured into waging the ‘war on terror’ since 9/11, but Isis, al-Qaeda and similar Salafi jihadi movements are far stronger now than they were then. They have powerful military forces fighting in at least seven wars – Afghanistan, Iraq, Syria, Yemen, Libya, Somalia, North East Nigeria – as well as in insurgencies, large and small, such as in Sinai and north-west Pakistan. Individuals and cells carry out terrorist attacks everywhere from Orlando to Baghdad and Berlin to Mogadishu.

Seldom has a war been so comprehensively and visibly lost as ‘the war on terror’ and it is doing a favour to Isis and al-Qaeda not to recognise this and try for something better. Yet critics of Corbyn have unconsciously been doing just such a favour to al-Qaeda by demanding he stay silent. In a crass but unintentionally revealing interview, the Conservative Security Minister Ben Wallace claimed that Corbyn’s timing was “appalling”. He said that “we have to be unequivocal, that no amount of excuses, no amount of twisted reasoning about a foreign policy here, a foreign policy there, can be an excuse. The reality is, these people hate our values.”

Manchester explosion in pictures Show all 37 1 /37 Manchester explosion in pictures Manchester explosion in pictures People running down stairs as they attempt to exit the Manchester Arena after a blast, where U.S. singer Ariana Grande had been performing, in Manchester Twitter/@ZACH_BRUCE/ via REUTERS Manchester explosion in pictures Helpers attend to people inside the Manchester Arena after a suspected suicide bomber detonated an explosive device at the end of an Ariana Grande concert, killing 22 people PA wire Manchester explosion in pictures Armed officers guard outside a hotel near the Manchester Arena following reports of an explosion, in Manchester, Britain EPA Manchester explosion in pictures Police officers are seen outside the Manchester Arena, where U.S. singer Ariana Grande had been performing, in Manchester, northern England Reuters Manchester explosion in pictures MANCHESTER, ENGLAND - MAY 23: Police escort members of the public from the Manchester Arena on May 23, 2017 in Manchester, England. An explosion occurred at Manchester Arena as concert goers were leaving the venue after Ariana Grande had performed. Greater Manchester Police have confirmed 19 fatalities and at least 50 injured. (Photo by Christopher Furlong/Getty Images) Getty Images Manchester explosion in pictures MANCHESTER, ENGLAND - Emergency services arrive close to the Manchester Arena on May 23, 2017 in Manchester, England. There have been reports of explosions at Manchester Arena where Ariana Grande had performed this evening. Greater Manchester Police have have confirmed there are fatalities and warned people to stay away from the area. (Photo by Dave Thompson/Getty Images) Getty Images Manchester explosion in pictures MANCHESTER, ENGLAND - MAY 23: Police escort members of the public from the Manchester Arena on May 23, 2017 in Manchester, England. An explosion occurred at Manchester Arena as concert goers were leaving the venue after Ariana Grande had performed. Greater Manchester Police have confirmed 19 fatalities and at least 50 injured. (Photo by Christopher Furlong/Getty Images) Getty Images Manchester explosion in pictures Medics deploy at the scene of a reported explosion during a concert in Manchester, England on May 23, 2017. British police said early May 23 there were "a number of confirmed fatalities" after reports of at least one explosion during a pop concert by US singer Ariana Grande. Ambulances were seen rushing to the Manchester Arena venue and police added in a statement that people should avoid the area / AFP PHOTO / Paul ELLIS (Photo credit should read PAUL ELLIS/AFP/Getty Images) AFP/Getty Images Manchester explosion in pictures Police and fans close to the Manchester Arena, after reports of an explosion Getty Images Manchester explosion in pictures There have been reports of explosions at Manchester Arena where Ariana Grande had performed Getty Images Manchester explosion in pictures Police deploy at scene of explosion in Manchester, England, at a concert in Manchester Arena AFP/Getty Images Manchester explosion in pictures Police stand by a cordoned off street close to the Manchester Arena Getty Images Manchester explosion in pictures Police deploy at scene of explosion in Manchester, England AFP/Getty Images Manchester explosion in pictures Police deploy at scene of a reported explosion during a concert in Manchester, England, on May 23, 2017. British police said early May 23 there were "a number of confirmed fatalities" after reports of at least one explosion during a pop concert by US singer Ariana Grande. Ambulances were seen rushing to the Manchester Arena venue and police added in a statement that people should avoid the area AFP/Getty Images Manchester explosion in pictures An ambulance drives away from the Manchester Arena, where U.S. singer Ariana Grande had been performing, in Manchester Reuters Manchester explosion in pictures Police escort members of the public from the Manchester Arena in Manchester, England. Getty Images Manchester explosion in pictures A woman sits in the street in a blanket near the Manchester Arena as police guard the area following reports of an explosion, in Manchester, Britain EPA Manchester explosion in pictures Two women wrapped in thermal blankets stand near the Manchester Arena, where US singer Ariana Grande had been performing, in Manchester Reuters Manchester explosion in pictures A Royal Logistic Corps (RLC) bomb disposal robot is unloaded outside the Manchester Arena following reports of an explosion, in Manchester. At least 19 people have been confirmed dead and others 50 were injured, authorities said. It is being treated as a terrorist incident until police know otherwise EPA Manchester explosion in pictures A Royal Logistic Corps (RLC) bomb disposal robot is unloaded outside the Manchester Arena following reports of an explosion, in Manchester EPA Manchester explosion in pictures Members of the public receive treatment from emergency service staff at Victoria Railway Station close to the Manchester Arena on May 23, 2017 in Manchester, England. There have been reports of explosions at Manchester Arena where Ariana Grande had performed this evening. Greater Manchester Police have have confirmed there are fatalities and warned people to stay away from the area Getty Images Manchester explosion in pictures Armed police after a suspected terrorist attack at the Manchester Arena at the end of a concert by US star Ariana Grande left 19 dead PA wire Manchester explosion in pictures Emergency services arrive close to the Manchester Arena in Manchester Getty Images Manchester explosion in pictures An amoured police vehicle patrols near Manchester Arena in Manchester Getty Images Manchester explosion in pictures A man carries a young girl on his shoulders near Victoria station in Manchester AFP/Getty Images Manchester explosion in pictures Police officers stand at the Miller Street and Corporation Street Crossroads, in front of the Manchester Arena in Manchester, England Getty Images Manchester explosion in pictures Police block a road near to the Manchester Arena in central Manchester, England AP Manchester explosion in pictures Armed police patrol near Victoria station in Manchester, northwest England. Twenty two people have been killed and dozens injured after a suspected suicide bomber targeted fans leaving a concert of US singer Ariana Grande in Manchester Getty Images Manchester explosion in pictures Police forensic officers leave the Manchester Arena as they investigate the scene of an explosion in Manchester Getty Images Manchester explosion in pictures A forensic officer collects evidence on a walkway between Victoria station and Manchester Arena following a deadly terror attack in Manchester, Getty Images Manchester explosion in pictures A woman and a young girl wearing a t-shirt of US singer Ariana Grande talks to police near Manchester Arena following a deadly terror attack in Manchester, Getty Manchester explosion in pictures epaselect epa05982725 Susan Walton and daughter Katie, 10 (pictured), who attended the concert of Ariana Grande at the Manchester Arena, are seen in Manchester, Britain, 23 May 2017. According to a statement released by the Greater Manchester Police on 23 May 2017, police responded to reports of an explosion at Manchester Arena on 22 May 2017 evening. At least 19 people have been confirmed dead and around 50 others were injured, authorities said. The happening is currently treated as a terrorist incident until police know otherwise. According to reports quoting witnesses, a mass evacuation was prompted after explosions were heard at the end of US singer Ariana Grande's concert in the arena. EPA/NIGEL RODDIS EPA Manchester explosion in pictures Mayor of Greater Manchester Andy Burnham and Manchester City Council Leader Sir Richard Leese speak to the media outside Manchester Town Hall after a suicide bomber killed 22 people, including children, as an explosion tore through fans leaving a pop concert in Manchester Dave Higgens/PA Wire Manchester explosion in pictures The media gather behind a police cordon in Manchester Getty Images Manchester explosion in pictures Flowers left close to the Manchester Arena, the morning after a suicide bomber killed 22 people, including children, as an explosion tore through fans leaving a pop concert in Manchester Danny Lawson/PA Wire Manchester explosion in pictures Ariana Grande concert attendees Karen Moore and her daughter Molly Steed, aged 14, from Derby, leave the Park Inn where they were given refuge after last night's explosion at Manchester Arena Getty Manchester explosion in pictures Signs saying 'We love Manchester' are displayed in a window in Manchester, England Getty Images

Of course, this is the old political gambit, often deployed by politicians and journalists, of deliberately mistaking explanation for justification. More significantly, Wallace repeats the mantra usually expressed after terrorist attacks, when political leaders promote national unity and emphasise mass mourning to the exclusion of almost anything else. After the killing of journalists at Charlie Hebdo magazine in Paris in 2015, some 40 world leaders walked through the streets in solidarity against terrorism. Such demonstrations are intended as a show of concern, but in practice they become a replacement for effective action.

Emotional outpourings, sincere or not, are politically convenient for governments because they divert attention from failed policies that may well have helped promote terrorist movements. Wallace is dismissive of “a foreign policy here, a foreign policy there” having any effect on terrorism, but the foreign policies most in question are those which led to Britain engaging in wars to overthrow Saddam Hussein in Iraq in 2003 and Muammar Gaddafi in Libya in 2011. Both wars succeeded in their aims, but they also led to a collapse of the Iraqi and Libyan states and opened the door to al-Qaeda, Isis and their clones.

It should be firmly said that, if Saddam and Gaddafi had not been overthrown, it is unlikely that Salman Abedi would have been in a position to slaughter people in Manchester.

There has been much controversy over Britain’s decision to join the invasion of Iraq, but not enough about its role in overthrowing Gaddafi eight years later. The nature of British participation in the Libyan war and the consequence of its actions deserve to be the subject of an inquiry as thorough as Chilcot’s. This is because the British participation went well beyond airstrikes and training of Libyan rebels. Reports are emerging that it involved energising and facilitating the movements of known Salafi-jihadi British Libyans and Libyan exiles who wished to return to Libya to fight Gaddafi. In other words, the Islamic jihadi networks of the type to which Salman Abedi and his family belonged acted as useful proxies for the British state.

Several Libyans in Britain had been subjected to “control orders”, a form of house arrest introduced after the bombings in London in 2005, to stop them going to fight in Iraq according to a detailed report in the online magazine Middle East Eye. Citing interviews with Libyan Islamic militants, it says that British authorities adopted an “open door” policy for Libyans willing to fight Gaddafi. “I was allowed to go, no questions asked,” said one source.