Garden Bridge deal was close to collapse in December
London's controversial Garden Bridge project came close to collapse last year, it has emerged.
Letters seen by the BBC show the chairman of the Garden Bridge Trust Lord Davies warned London mayor Sadiq Khan "full participation" was needed at the project's "critical stage".
Mr Khan refused to guarantee the project, arguing that further funding was still required for it to go ahead.
On Friday, Dame Margaret Hodge's review recommended scrapping the plan.
She said it would be better to ditch the project than risk uncertain costs.
The bridge was given mayoral support under the Conservative mayor Boris Johnson who left City Hall in May last year.
But a "mayoral guarantee" had not been completely signed off.
In letters released under a Freedom of Information request, Lord Davies said this was the basis upon which the trustees were able to pursue private and public funding.
In a letter sent on 9 December, Lord Davies lobbied Labour mayor Mr Khan to provide the same guarantees offered by his predecessor.
He said: "Without your public support, I cannot see that this project can proceed", adding "I plead with you to engage with me to find a way forward".
"You have explained that the previous mayor's commitment ceases to be relevant and you cannot allow any guarantees to be entered into unless you are satisfied that this will not lead to further public expenditure down the line."
Lord Davies also criticised Dame Margaret's review being set up, claiming it gave "a degree of uncertainty" about the project and damaged "the trust's ability to raise the balance of the funds required from the private sector".
In response Mr Khan stood firm, insisting he would not give a guarantee without "proper consideration" of the business plan but he did reaffirm his view that the bridge should be built.
"I believe that the position that I set out in May is clear given previous expenditure, the taxpayer will be better off if the bridge is built," the mayor said.
On Friday, a spokeswoman for the Garden Bridge Trust said: "We have always been clear about the challenges that the Trust has faced since last summer when it put its contractors on standby. We made that clear in our accounts filed with Companies House in January."
She said the trust was still hopeful the mayor would still sign a maintenance guarantee - a next step to a business plan - and that trust and City Hall officials would meet after Easter.