The fallout from the damning report into the invasion and occupation of Iraq continued as Foreign Secretary Philip Hammond faces questioning on the implications of the devastating findings for Britain's future role in the world.
Mr Hammond will appear before the influential Commons select committee on foreign affairs as the impact of Sir John Chilcot's searing indictment of the build-up and execution of the war rocked the political and intelligence establishment.
The move came as former prime minister Tony Blair was put on notice by families of dead servicemen that he faces legal action over what flowed from his fateful decision to tell then US president George Bush "I will be with you whatever" eight months before the 2003 invasion.
A defiant Mr Blair refused to accept accusations from service families that he had been wrong and reckless as he insisted he would make the decision to go to war again if presented with the same information about the threat posed by Iraqi dictator Saddam Hussein at the time.
Mr Blair's stance was at odds with the report's finding that war was not the last resort, but that Britain triggered military action before all options for a peaceful resolution to the crisis had been exhausted.
Families of some of the 179 military personnel killed in Iraq described the former prime minister as a "terrorist", and Jeremy Corbyn offered an apology on Labour's behalf for what he branded "a stain on our party and our country".
Mr Blair insisted he could look the families in the eye - and the nation - and state that he did not mislead anyone over the invasion, the service personnel did not die in vain, and he was right to do what he did.
The long-delayed Chilcot report insisted that Saddam posed "no imminent threat" at the time of the invasion, and the war was unleashed on the basis of "flawed" intelligence.
And in a withering assessment of its aftermath, the probe found the military intervention ended six years later "a very long way from success", with the "humiliating" spectacle of UK troops in Basra making deals with local militia who had been attacking them.
Mr Blair said he took responsibility for "mistakes in planning and process" identified by the report, and felt "more sorrow, regret and apology than you may ever know" for the grief of those whose loved ones died.
Key findings in the 2.6 million-word report included:
:: The case for war was presented with "a certainty which was not justified";
:: It was based on "flawed" intelligence about the country's supposed weapons of mass destruction (WMD) which was not challenged as it should have been;
:: The US-led coalition resorted to force to remove Saddam before peaceful options for disarmament had been exhausted and in a way which undermined the authority of the United Nations Security Council;
:: Planning for post-conflict Iraq was "wholly inadequate", with shortfalls in armoured vehicles to protect UK troops which "should not have been tolerated".
:: The risks of military action were "neither properly identified nor fully exposed to ministers" and the UK took on responsibility for four provinces of southern Iraq "without ensuring that it had the necessary military and civilian capabilities to discharge its obligations".
The report did not support claims that Mr Blair agreed a deal "signed in blood" to topple Saddam at a key meeting with Mr Bush at his ranch in Crawford, Texas, in 2002.
But it revealed that in July that year - eight months before Parliament approved military action - the PM committed himself in writing to backing the US president over Iraq, telling him: "I will be with you whatever."
The probe also strongly rejected Mr Blair's claims that the bloody insurgency and terrorism which erupted following Saddam's fall could not have been foreseen.
Military policeman's father Reg Keys said it was clear that Mr Blair "deliberately misled" the country and that his son Tom "died in vain", while Roger Bacon, whose son Matthew was killed by a roadside bomb, said the families reserved the right "to call specific parties to answer for their actions in the courts".
Sarah O'Connor, whose brother Bob died when a military plane was shot down near Baghdad in 2005, branded Mr Blair "the world's worst terrorist".
While the Chilcot Report contained "serious criticisms", it showed that "there were no lies, Parliament and the Cabinet were not misled, there was no secret commitment to war, intelligence was not falsified and the decision was made in good faith", it said.
But while shadow cabinet minister Paul Flynn said prosecution of Mr Blair should be "seriously considered", Labour leader Mr Corbyn stopped short of calling for his predecessor to be tried for war crimes, as some had expected.