Revealed: the garden bridge planned by Thomas Heatherwick and Joanna Lumley is not actually going to be open to all. Instead it will be a privately-managed tourist attraction likely to require advance booking

“It will set hearts racing and calm troubled minds,” according to the garden bridge’s chief promoter, Joanna Lumley. “It will enchant everyone who uses it.” But not, it turns out, if you’re in a group of eight or more, or if you want to ride a bicycle, or visit Thomas Heatherwick’s bridge by night – and certainly not if you’re planning a protest.

Having received planning permission from Lambeth council last week – the first hurdle in a process that will be followed by Westminster’s decision next month, before swooshing across the mayor’s lubricated planning desk then passing under the nose of Eric Pickles – a series of conditions has emerged that make the project look rather less public than first imagined.

“All groups of eight or more visitors would be required to contact the Garden Bridge Trust to request a formal visit to the bridge,” states Lambeth council’s planning report to its committee, which recommends conditional planning. “This policy would not only assist visitor management but also would discourage protest groups from trying to access the bridge.”

Such a measure suggests that the garden bridge, as its critics have suspected, is not in fact a bridge – in the sense of being a public right of way across the river – but another privately managed tourist attraction, on which £60m of public money is to be lavished. A limit on group sizes suggests a ticketing system will have to be put in place.

As Building Design magazine reports, further details about the bridge have emerged, including expected visitor numbers of 7.1m a year, with peak crowds of 30,000 on a Saturday – for a bridge that has a capacity of 2,500 people. It will also be closed once a month for fundraising events, and shut between midnight and 6am, somewhat scuppering Lumley’s vision of late-night trysts.

Anyone hoping to nip across on a bike will be foiled, too. “Cyclists would be able to push bikes over but not ride,” states the report. “If cyclists were allowed to ride, to provide a safe pedestrian environment it would be necessary to incorporate segregated cycle lanes or wider shared paths. This would result in a much reduced planted area and erode the benefits of the bridge as a green space.”

Many doubt the claimed bounty of green space in the first place. The area of the bridge is around 6,000 sq m, but the plans show about 2,700 sq m as planted area – less than half the size of a football pitch. Thames Central Open Space campaign group also points out that 30 trees are to be cut down on the south bank to make way for the bridge’s hefty landing podium, a substantial building “designed as a flexible structure to accommodate a number of uses,” which will most likely end up housing retail.

Critics are calling for a public inquiry into this grand mayoral project of most opaque origins, which appears to have been fast-tracked through the system, and planned for a site where there are already four bridges within just over a mile of each other – when crossings are desperately needed further east.

But rest assured, if Heatherwick’s magic mushrooms don’t sprout in London, you can always go and see his forest of fungi in New York.