“Russian interests have comprehensively penetrated the Conservative Party,” claims the author and Guardian foreign correspondent Luke Harding, one of many guests invited to speak on a “kleptocracy tour” of London – a charabanc organised by anti-corruption campaigners Roman Borisovich and Arthur Doohan. Other esteemed guests included investigative journalist Carole Cadwalladr, Labour MP Margaret Hodge and author Oliver Bullough. They took it in turns to play the role of tour guide at the front of the bus, as the press corps listened to the escapades of numerous oligarchs.

“Poyekhali,” said Borisovich, switching to his native tongue to invoke the spirit of Yuri Gargarin. “Our trundling rocket will take us through the streets of London. We’re rolling.”

Like any good John le Carré novel, the day was full of twists and turns, riddles and red herrings. At one particularly surreal point, we were stuck in traffic outside New Broadcasting House, as the foreign policy hawk Edward Lucas assessed the Russian-speaking capabilities of the Metropolitan Police. Then, outside the Foreign Secretary’s official residence overlooking St James’s Park, the veteran investigative reporter John Sweeney was dialled in from his self-imposed coronavirus quarantine.

There was an underlying pattern to the stories: Russians with close ties to Vladimir Putin’s security services have consistently bought not just property and assets in London, but also political influence by donating to the UK’s main parties. Only last week, new data released by the Electoral Commission showed that Lubov Chernukhin, the wife of a former Putin cabinet minister, contributed £200,000 to the Conservative Party’s election war chest in November 2019. In 2014, Chernukhin was reported to have paid £160,000 at a fundraising event to play tennis with David Cameron and Boris Johnson.

“The British ruling class has shown itself to be up for sale,” said Bullough as we wound through the tight streets of Belgravia.

Doohan and Borisovich’s tours, once regular affairs, have undergone a partial hiatus in recent years. The continued delay in releasing the Intelligence and Security Committee’s report on the potential threat from Russia has prompted their return. In truth, the report is unlikely to yield any great conspiracy, and it may well be that the government has done itself more harm than good by witholding publication for so long. Rumours continue to circulate that might have been put to rest.

[See also: Will Boris Johnson release the Russian interference report after the cabinet reshuffle?]

But those on the bus were living proof that journalism and campaigning can affect the law. Unexplained Wealth Orders came into force in 2018 and took their first scalp last year when Zamira Hajiyeva, the wife of an Azerbaijani banker imprisoned in his homeland for theft, was forced to explain how she could afford a £16m spending spree at Harrods. Meanwhile, the net is tightening around offshore havens. Overseas territories such as the British Virgin Islands and crown dependencies such as Guernsey will have to publish registers of beneficial ownership by 2023 – a way of clamping down on money laundering.

“You can't create a strong economy on dirty money,” said Hodge, a little windswept as she hopped on the bus at Westminster to give a rousing final statement.

The tour was a chance to highlight the implications for our security, economy and politics if we continue to allow London to be the money-laundering capital of the world. While the Russia report may not contain the damning material that some government critics are hoping for, it is worth paying attention to the tour guides – for they are the ones investigating possible corruption in imaginative ways, and are contributing to gradual changes in our law.

[See also: Moneyland: how the super-rich looted their own countries to create an elite global haven]

Clarification: an earlier version of this article referred to Alexander and Evgeny Lebedev. We acknowledge that we should not have included them in the article and apologise for this error.