The remains of five former Archbishops of Canterbury have reportedly been discovered beneath a church.
"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.
Experts have identified one of those buried there as Richard Bancroft, who served as Archbishop of Canterbury from 1604 to 1610 and oversaw the publication of a translation of the bible into English.
Some 30 lead coffins were found as builders tried to flatten the floor in the chancel of St Mary-at-Lambeth to create an exhibition area for the Garden Museum, next to Lambeth Palace.
Other archbishops were believed buried in the vault are Frederick Cornwallis (in office 1768-1783), Matthew Hutton (1757-1758) and Thomas Tenison (1695-1715).
Experts are still working to establish who else may be buried in the crypt.
Garden Museum director Christopher Woodward said: "We know there are five archbishops buried here".
The church St Mary-at-Lambeth was originally built in the 11th Century.
Mr Woodward said: "This church had two lives: it was the parish church of Lambeth, this little village by the river...but it was also a kind of annex to Lambeth Palace itself".
"And over the centuries a significant number of the archbishops" households chose to worship here and to be buried here'.
Speaking about the development, Mr Woodward said: 'This is one of the most sacred and precious sites in London. The church was located next to the Thames and could be flooded, and the Victorians had already cleared out thousands of coffins when they remodelled the building in the 19th century.
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.
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.