We knew things were serious in the House of Commons when Liz Truss appeared. She had, before Monday, spoken only three times since her triumphant half-term in office was brought to an end by a left-wing conspiracy of Conservative MPs and bond traders. But here she was, taking a seat on the far distant backbenches.

There too was her arch-enemy and sometime Chevening House-sharer Dominic Raab, looking very tanned, presumably as a result of not having had to interrupt his holiday to rescue any pets from the Taliban. Great matters, we knew, must be afoot.

Dowden is, sadly, poorly cast as Harry Palmer or George Smiley

They had come to hear news of a dastardly plot against the very body of which they are members — an apparent attempt by a hostile power to infiltrate parliament. Who was behind it? Was it the Anti-Growth Coalition that Truss last year identified as the greatest danger to Britain? Or was it the civil service blob that had conspired to bring down Raab in the summer, with their complaints about flying tomatoes and document formatting requests?

It was in fact, Deputy Prime Minister Oliver Dowden said, the Chinese. British security services were, he announced, investigating whether a parliamentary researcher had been spying on China’s behalf. (The man in question has, it should be said, issued a statement strongly denying this.)

Dowden is, sadly, poorly cast as Harry Palmer or George Smiley. Neither menace nor gravitas are really in his range. The best we can say is that any Chinese officials watching his statement will have been left in no doubt that His Majesty’s Government is really peeved about all this. “We are clear-eyed” about the “challenge” posed by China, he said, sounding like a deputy headmaster discussing an especially awkward sixth-former.

“We are in the front line of this threat,” he intoned, standing 5,000 miles away from Beijing

He listed all the ways the government had been tough, pointing to his own banning, when he was Culture Secretary, of Huawei from British 5G systems. Unfortunately, many of those present could recall the distinct reluctance with which he had been pushed into that decision. Among those who twisted his arm at the time was Tom Tugendhat, now security minister and sitting just down the front bench from Dowden. The current scandal is a touch awkward for Tugendhat, as the arrested researcher had worked alongside him before he joined the government.

It’s not entirely clear why the Chinese would have felt the need to hire a spy to find out Tugendhat’s views, which have broadly been available to anyone who phoned and asked for them. Nor indeed, was there anything secret about the attitude of most of the Tory backbenchers who spoke, that China is a threat to Britain and needs to be confronted. It is, however, less clear whether this is also the view of Rishi Sunak.

Julian Lewis, chair of the Intelligence and Security Committee, pointed out that the government had recently downplayed the idea that China was a threat. Dowden was evasive. Lewis looked unimpressed. This set the pattern. Truss said China was “the greatest threat both to the world and the UK”. Dowden replied that the country was “a systemic challenge”.

Perhaps sensing this wasn’t enough, he went further, saying the country was “the number one state-based threat to our economic security”. They still weren’t happy. Iain Duncan Smith said the government was in a “mess” on the subject. “Are they a threat or are they not?” he demanded. The government regularly raised matters of concern with the Chinese, Dowden replied. It doesn’t seem to be doing the trick.

And then we got to the real victims. Tim Loughton, a Tory who is the subject of Chinese sanctions, rose to his feet. “We are in the front line of this threat,” he intoned, standing 5,000 miles away from Beijing.

And not just him, Labour’s Barry Gardiner, one of whose staff was last year accused of being the son of a Chinese agent, spoke. “Can I extend my genuine sympathy to the two Conservative colleagues who appear to have been targeted by a suspected Chinese spy?” he began. Tugendhat’s hand moved to cover his face. “I do know what they’re feeling,” Gardiner went on, although had that in fact been the case, he would probably have stopped speaking.

We looked at Alicia Kearns, the other Tory who’d had contact with the arrested researcher. As with Tugendhat, the idea that you would need a spy to tell you what she was thinking is surprising at any time. But as Gardiner spoke, she gave him a stare whose meaning was so plain and intense that it required no codebreakers.

Gardiner, though, ploughed on oblivious, offering a defence of his own situation. There may be some people who are beyond the help of any intelligence service.