The former London mayor and his chums squandered £22m on a vanity project

The publication of the National Audit Office report into the Garden Bridge is yet another nail in the coffin of this doomed vanity project. The damning report found that ministers ignored civil service advice, that the project did not represent value for money, and that taxpayers stand to lose more than £20 million if it is cancelled.

The sorry saga of the Garden Bridge is a strange tale of a quintessentially British style of corruption. Not corruption in the sense of backhanders, personal enrichment or bribery, but a sort of cocktail party cronyism. A group of powerful, well-connected individuals – politicians, celebrities, designers and a few journalists – decided it would be a jolly nice thing to have, and set about using their positions to rig the system to make sure it went ahead. Transport for London (TfL) set up a procurement process that ensured the Heatherwick design was chosen. Ministers ignored the advice of senior civil servants that the project did not represent value for money. Some of London's media ran gushing, one-sided stories extolling the wonders of the project. Even the then Prime Minister personally intervened to ensure its government credit line was secured.

But “nice to have” is not a basis for public spending, so the Garden Bridge always found itself to be a project in search of justification.

The original pretext was that it was a transport project. TfL produced a business case for a pedestrian footbridge between Temple and the South Bank. I have previously written about the rigged procurement process for this bridge which ensured that Heatherwick Studios' design for a garden bridge was chosen over designs for what was actually tendered for – an ordinary pedestrian footbridge. The Garden Bridge serves no real transport purpose: it would be closed at night, difficult to walk through quickly, closed for various corporate events and not open to cyclists. The supposed transport case was always a ruse. London needs more river crossings, but we need them east of Tower Bridge.

Then came the tourism argument. We needn't spend too much time on this one: the South Bank is already one of the most popular and congested tourist attractions in London. Bringing more tourists to an already saturated area is not a sensible tourism strategy. Instead, you maximise a city's benefits from tourism by dispersing tourists to other areas, thus maximising your potential economic benefit.

The argument that the Garden Bridge would be a catalyst for regeneration on the South Bank was a particularly desperate one. The district which includes the National Theatre, the BFI and the Southbank Centre would not be top of the list of areas that you'd think would need regenerating. That said, poverty and deprivation exist throughout London including in some of the parts one would least expect. However, ask the local community in Waterloo what they'd like £40 million of public cash spent on in their area, and I bet none of them will say “a garden on a bridge”. Indeed, the community around the South Bank has opposed the bridge from the start.

I don't believe that this bridge will ever be built. The start of construction has been pushed back by 18 months and the main contractor has been put on standby. A recent Newsnight investigation identified a £52m funding gap. The project is now so tainted by the whiff of scandal that I find it hard to believe that further private sponsors will wish to be associated with it. Indeed, several have dropped out of the project having initially pledged cash. Theresa May's government is far less well disposed to this sort of extravagance than Cameron's. Mayor Sadiq Khan has launched an official inquiry into the project under the fearsome former Public Accounts Committee Chair Dame Margaret Hodge. To guarantee no further public spending on the bridge I've called on the Mayor not to sign the guarantee that City Hall would underwrite its annual running costs if the Garden Bridge Trust can't raise funds.

Nearly £40 million of taxpayer cash has been poured into the Thames with nothing to show for it but a glossy website, a series of damning reports and a furious local community. We are witnessing the slow, expensive death of the Garden Bridge. It would be better to put it out of its misery sooner rather than later.

I don't believe that anyone associated with the Garden Bridge project has done anything that would see them taken to court. However, the court of public opinion will not look kindly on those who frittered away tens of millions of pounds of taxpayer's cash on a vanity project that never happened.