Following the damning Chilcot report, much will be said about the decision to go to war in Iraq. But one thing will be missing: the information I leaked in the runup to the war. It won’t get an airing because I was never questioned or asked to participate in the Chilcot inquiry.

Back in early 2003, Tony Blair was keen to secure UN backing for a resolution that would authorise the use of force against Iraq. I was a linguist and analyst at GCHQ when, on 31 Jan 2003, I, along with dozens of others in GCHQ, received an email from a senior official at the National Security Agency. It said the agency was “mounting a surge particularly directed at the UN security council (UNSC) members”, and that it wanted “the whole gamut of information that could give US policymakers an edge in obtaining results favourable to US goals or to head off surprises”.

In other words, the US planned to use intercepted communications of the security council delegates. The focus of the “surge” was principally directed at the six swing nations then on the UNSC: Angola, Cameroon, Chile, Bulgaria, Guinea and Pakistan. The Chilcot report has eliminated any doubt that the goal of the war was regime change by military means. But that is what many people already suspected in 2003.

I was furious when I read that email and leaked it. Soon afterwards, when the Observer ran a front-page story: “US dirty tricks to win vote on Iraq war”, I confessed to the leak and was arrested on suspicion of the breach of section 1 of the Official Secrets Act. I pleaded not guilty and, assisted by Liberty and Ben Emmerson QC, offered a defence of necessity – in other words, a breach of the law in order to prevent imminent loss of human life. This defence had not and, to my knowledge, has still not, been tested in a court of law.

I believed that on receiving the email, UK MPs might question the urgency and motives of the war hawks

I believed that on receiving the email, UK parliamentary members might question the urgency and motives of the war hawks, and demand further deliberations and scrutiny. I thought it might delay or perhaps even halt the march towards a war that would devastate Iraqi lives and infrastructure already crushed by a decade of unrelenting sanctions. A war that would send UK and US service men and women into harm’s way, leaving hundreds of them dead, disfigured and traumatised. Unfortunately, that did not happen. It couldn’t, for now we know via Chilcot that Blair promised George W Bush he would be “with him, whatever”.

It took eight months before the Crown Prosecution Service announced I would be charged. It had a change of heart two and a half months later, after my legal team demanded to see all the legal advice to Blair in the runup to the war. I left the Old Bailey with a huge weight gone from my shoulders. It was a day I will never forget.

Chilcot’s report does not apportion blame. But it does provide ample evidence of what many of us knew all along: that this was an illegal war, that military intervention was by no means a last resort, that all avenues were not exhausted and that Iraq posed no immediate threat to the UK. Furthermore, the post-invasion plan for Iraq looked like it had been scribbled on the back of a beer mat. Blair was warned by the intelligence services that the threat levels to the UK would increase, that Iraqi weapons would fall into the hands of al-Qaida. The consequences of his lack of concern about these things can be felt to this day.

We know a lot more now than we knew before, but what about the email I leaked? Who did the NSA talk to in the UK to OK it? Did it talk to anyone? How did an NSA official feel bold enough to write to UK civil servants anticipating their cooperation in an attempt to undermine the UN’s diplomatic processes, in a secret effort to garner information to secure “results favourable to US goals”? How far did the surveillance operation proceed? Whose communications did they intercept and record? What, if anything did they discover and did they use any information they may have gathered? Was this email sent to other organisation or agencies besides GCHQ? It seems reasonable to ask why this crucial information was not included in the Chilcot inquiry?

It was a huge relief when the CPS dropped its charges. But I had admitted the leak. Why did it decline to offer evidence? The catastrophe of the Iraq invasion and occupation is painfully evident today. Terrorism and risk has spread across the globe as many said it would. So much for “keeping us safe” and protecting our freedoms.

Chilcot has shone a light on what happened, but it is clear there are still bits of the puzzle that are missing. Now that we know better, will we do better?