Boris Johnson is facing a grilling over his handling of the Garden Bridge project during his time as London mayor.
The Foreign Secretary will be questioned about his involvement in the controversial scheme by the Greater London Authority's (GLA) oversight committee on Thursday.
The GLA said the appearance marked the first time the London Assembly had used its summons powers on a former mayor.
Mr Johnson backed the scheme for a landscaped pedestrian Thames crossing while he was in City Hall, but Labour successor Sadiq Khan effectively killed off the idea.
The much talked about initiative had been championed by Absolutely Fabulous star Joanna Lumley but was abandoned amid bitter recriminations over the use of taxpayers' cash.
Mr Khan said in April 2017 he would not provide guarantees for the planned bridge because it would leave taxpayers in the capital at risk of higher bills.
More than £37 million of public money had already been spent on the project.
The move followed a damning report by Dame Margaret Hodge that recommended dropping the proposed Thames crossing because it was "difficult to justify further public investment" in the bridge, which was likely to end up costing more than £200 million.