The remains of five archbishops of Canterbury have been found inside a secret tomb underneath a church, in a discovery hailed as "astonishing".
St Mary-at-Lambeth Church, next to Lambeth Palace, the official London residence of the Archbishop of Canterbury, is currently home to the Garden Museum.
Just over a year ago, while builders were renovating the de-consecrated medieval parish church, they discovered an entry to a hidden crypt as they lifted up some slabs.
Speaking in a video which the Garden Museum posted online, Karl Patten, site manager of Rooff Ltd, said the find amounted to a "very interesting day".
"We were exposing the ground as part of the job and we were lifting the slabs in the arc area and we uncovered an entry to what looked like a tomb," he said.
"We got a camera on the end of a stick and discovered numerous coffins and one of them had a gold crown on top of it."
Christopher Woodward, director of the Garden Museum, said the multi-million renovation works were going "incredibly smoothly" until he received an urgent call from Mr Patten.
"I came in thinking this sounds like bad news, problem, and wow, and it's the crown, it is the mitre of an Archbishop gleaming there in the dark," he added.
Mr Woodward revealed in the video there are five archbishops buried in the tomb.
He said one of these is Richard Bancroft, who became archbishop in 1604, and who chaired the committee that wrote the King James Bible, published in 1611.
Bancroft and John Moore were identified by the name plates on the coffins, and the museum said they believe Frederick Cornwallis, Matthew Hutton and Thomas Tenison are also inside.
With at least 20 coffins identified, Mr Woodward said they "still don't know who else is down there".
Wesley Kerr, former chairman of the Heritage Lottery Fund London, said the find is "really astonishing" and "one of the most incredible" things he has seen.
"To know that possibly the person that commissioned the King James Bible is buried here is the most incredible discovery and greatly adds to the texture of this project," he added.
Mr Woodward said they "knew there was no crypt, because it is so close to the Thames that it would have flooded".
"We also knew that in the 1850s when the Victorians remodelled the church, they pretty much cleared hundreds if not thousands of coffins out to make this new building with underfloor heating," he added.
Mr Woodward said "every archaeologist in London" has looked at the building and that "no one told them to expect to find anything" during the renovation works.
The museum began in 1977 in a bid to stop the church of St Mary's and the burial place of John Tradescant, considered the first great gardener in British history, from being demolished.
Focusing on the design, history and culture of gardens; in 2008 galleries, exhibition and education spaces were created as part of the first phase of the museum's transformation.
In October 2015 it closed for 18 months to allow building restoration works to take place, as well as the extension of existing gallery space and the creation of a new garden.
Supported with a grant from the Heritage Lottery Fund, the Garden Museum said the £7.5 million redevelopment is expected to be completed this spring.