For some time now cabinet meetings might as well have taken place in public. Just on a slight time delay, now that ministers have their phones confiscated on arrival to stop them leaking details of proceedings in real time. But within minutes of them being reunited with their mobiles, trusted journalists are given a full briefing. No detail goes unrecorded. Who quarrelled with whom. Who made a fool of themselves. Who ate the most biscuits. Who had one too many double espressos. Whether the prime minister voiced any opinion on anything.

But while passing on details of the ongoing cabinet-level disagreements over Brexit is now considered fair game – if not a public service – ministers have drawn the line at liveblogging matters of defence and national security. Until now. Moments after Tuesday’s meeting of the National Security Council, at which top military brass and spooks provide intelligence to selected members of the cabinet, had been wrapped up, the Daily Telegraph was running a story on how Theresa May was planning to weaken Britain’s cyber-defences by outsourcing parts of the new 5G network to the Chinese state-controlled tech firm Huawei.

The leak was quickly narrowed down to one of the five cabinet ministers who had spoken out against Huawei at the NSC meeting. Sajid Javid, Jeremy Hunt, Gavin Williamson, Penny Mordaunt and Liam Fox. Mordaunt and Fox were quickly eliminated, mainly on the grounds that they are considered to be of no importance. Or use. Even to themselves. Of the other three, it is the defence secretary who is the prime suspect.

Like Javid and Hunt, Williamson is keen to big up his leadership credentials by sounding hawkish over China, but only he might be considered stupid enough to imagine no one would notice what he’d done and that there would be no comeback. Don’t tell them, Private Pike! Much more of this and the security services won’t dare provide the cabinet with any information for fear the rest of the world will soon be able to track all our spies on their phone via a customised Ministry of Defence app.

Q&A What is Huawei and why is its role in 5G so controversial? Show Fast-growing Huawei is arguably China’s first global multinational. The Shenzhen-based company makes mobile phones, base stations and the intelligent routers that facilitate communications around the world. But its success increasingly concerns the US, which argues Huawei is ultimately beholden to the Chinese Communist party and has the capability to engage in covert surveillance where its equipment is used. Huawei is by some distance the world’s largest supplier of telecoms equipment with an estimated 28% market share in 2019. It was also the second largest phone maker in 2019, after Samsung and ahead of Apple. But Australia banned Huawei from 5G in 2018, with its spy agencies declaring they were worried the company could shut down power networks and other parts of its infrastructure in a diplomatic crisis. Trump banned US companies from working with Huawei last year and has strenuously lobbied others to follow suit, venting “apoplectic fury” in a phone call to Boris Johnson after the UK agreed to allow the Chinese company into 5G. The company had successfully targeted the UK early on. It has supplied BT since 2003 and gradually expanded to the point where it agreed to create a special unit in Banbury, known as the Cell, where the spy agency GCHQ could review and monitor its software code. Vodafone is another key customer. Britain’s intelligence agencies said in January that any Huawei risk could be managed as long as the company was not allowed to have a monopoly. As a result, Boris Johnson concluded Huawei’s market share should be capped at 35% for forthcoming high-speed 5G networks. In July 2020 the UK position changed, and it was announced that Huawei is to be stripped out of Britain’s 5G phone networks by 2027. Oliver Dowden, the UK culture secretary, also announced that no new Huawei 5G kit can be bought after 31 December 2020 – but said that older 2G, 3G and 4G kit can remain until it is no longer needed. Dan Sabbagh Defence and security editor Photograph: Mark Schiefelbein/AP

The official line from Downing Street has been that the leak is an unexplained – if regrettable – event that no one should worry their pretty little heads about too much. So Labour’s Jo Platt, shadow minister for the Cabinet Office, tabled an urgent question demanding more information. Just how did the leak occur and who was responsible? And why was Huawei even being considered? Even if it was possible to restrict the Chinese firm to 5G areas that didn’t affect security, the National Cyber Security Centre had declared its current technology to be sub-optimal and that it would be at least three to five years before it had anything usable.

Jeremy Wright, the secretary of state for culture, media and sport, sighed. Even though he was one of the few members of the cabinet who was definitely in the clear, it was no fun having to clear up other people’s mess. He wasn’t going to comment on the leak, he said, other than to agree that it shouldn’t have happened.

Nor did he want to prejudice any future investigation. If there were to be one. Though on the whole he thought investigations into leaks were counterproductive because they risked the possibility of someone actually uncovering the truth. And then the prime minister would have to sack the minister involved and it would all be very embarrassing. Far better to do nothing and hope the whole thing blew over. Then we could all pretend nothing had ever happened.

Jeremy Wright answers an urgent question on the leak. Photograph: House of Commons/PA

It was also important to remember, Wright insisted, that though the leak was 100% accurate it had been spun in an extremely unfavourable light. What had been decided wasn’t an actual decision. It was more of a meta decision. One that didn’t properly exist until it had been officially announced. And this official confirmation, that he wasn’t denying, of a confidential discussion didn’t quite count. He scratched his head and sat down. He hadn’t even managed to convince himself.

Wright didn’t have to wait long for the inevitable pile-on. Labour MPs were quick to point out that there was no area of public life in which the Tories could be trusted. Having screwed up Brexit and forced huge numbers of people into using food banks, the government was now leaking matters of national security. Jeremy Corbyn may not want to use nuclear missiles but at least he wouldn’t tell everyone where our subs were.

Conservative MPs were just as outraged. Tom Tugendhat, chair of the foreign affairs select committee, observed that the whole point of 5G technology was that there was no division between core defence and non-core activities, so there was no point imagining the Chinese would only have access to part of the network. Selling ourselves to the cheapest bidder was no way to run national security. Wright groaned. The whole episode was another clusterfuck. Regrets? He had a few. Too right he did. But he’d done what he had to do. And most of all, he’d done it Huawei.