The remains of five archbishops have been discovered in a tomb beneath a London, U.K. church, which now houses the Garden Museum, according to a press release.

Twenty coffins were discovered, according to the Garden Museum, two of which held the remains of Archbishops of Canterbury Richard Bancroft and John Moore. Bancroft chaired the committee that wrote the King James Bible in 1611.

The museum also identified two other people in the vault: John Bettesworth, the Dean of Arches – the judge who sits at the ecclesiastical court of the Archbishop of Canterbury – and Moore’s wife, Catherine Moore. According to the Telegraph, the church’s records show that the three remaining archbishops could be Frederick Cornwallis, Matthew Hutton, and Thomas Tenison.

“What we don’t know, what we still don’t know, is who else is down there,” Christopher Woodward, director of the Garden Museum, said in a video posted online.

Karl Patten, the site manager, said the vault was discovered when concrete slabs were being lifted from the floor of the church of St Mary-at-Lambeth. Below one of the slabs, some of which weighed up to 1,500 kg, was an entryway which “looked like a tomb.”

After a camera was placed on the end of a stick and lowered into the entryway, Patten said he saw “numerous coffins and one of them had a gold crown on top of it.”

The discovery of the vault was surprising, Woodward said, because the church is located so close to the Thames and such a structure could have easily been flooded. On top of that, the Victorians had cleared out “hundreds if not thousands of coffins” in the 19th century while remodeling the building.

“Every archeologist in London has looked at this building but no one had told us to expect anything,” Woodward said.

The church of St Mary-at-Lambeth, next to the Archbishop of Canterbury’s official London residence, was built by the sister of Edward the Confessor in the 11th century, Woodward said. It was scheduled to be demolished in the 1970s but a group of volunteers and garden historians worked to save it, and have it dedicated to John Tradescant, the gardener to King Charles I, who was buried in the church.

The Garden Museum closed in 2015 to undergo a $12 million redevelopment project. When the space reopens in the Spring of 2017, it will include a larger gallery space, new educational facilities, and a public garden. The museum will have five new galleries, Woodward said, and over 1,000 objects on display.

According to the museum’s website, it will also “interpret and explain the history of our building and neighbourhood, and the people who are buried here.”

“To know possibly that the person who commissioned the King James Bible is buried here is the most incredible discovery and greatly adds to the texture of this project,” said Wesley Kerr, chair of the Heritage Lottery Fund London between 2007 and 2014.