Before yesterday, it was hard to imagine Westminster gripped by any topic bar the fate of the Prime Minister. Then came the revelation that Parliament had been infiltrated by a Chinese spy, Christine Lee, who has channelled hundreds of thousands of pounds to the office of the Labour MP and Jeremy Corbyn ally, Barry Gardiner.

The security notice issued by MI5, warning other MPs of her attempts to “ensure the UK political landscape is favourable to the Chinese Communist Party’s agenda” dumbfounded many, including Sir Iain Duncan Smith, who has revealed in the past that he has been a target of Chinese threats for his support of sanctions against those involved in Beijing’s awful repression of Uyghur Muslims. Sir Iain asked three important questions: Why is no further action being taken against Ms Lee, who is not being deported? Did she get access to information – such as the details of Hong Kong refugees – which could put lives at risk? And perhaps most significantly, will there be an overhaul of security procedures at Westminster?

It is clear that the last two points merit investigation, for Ms Lee has been active across the political spectrum for many years, featuring in photos alongside Ken Livingstone and receiving an award from Theresa May. Even Lib Dem leader Ed Davey has received money from her. How many other MPs beyond Gardiner – who denies wrongdoing and says he has been in close contact with the security services – has she been close to?

In an environment in which MPs – rightly – can be accused of sleaze for relatively small transgressions, it is incredible that such influence trading can take place openly and apparently above board in Parliament. An urgent review is now required not just into the extent of Ms Lee’s meddling, but also into how it was allowed to occur in the first place, then endure for so long. Parliamentary authorities urgently need to explain themselves.

The affair is both embarrassing and potentially threatening, if Lee has managed to acquire sensitive information held on the Westminster estate. But in one way it is also useful, as a reminder of China’s true nature. Only three years ago, Lee posed outside No 10 to celebrate a “golden era” of Sino-British relations. The scandal which she has just detonated is more evidence that the years ahead are likely to be anything but.