The Dean of Chelmsford, the Very Reverend Peter Judd, said the diversity of the building was the reason for the change in status.
“Some of the architecture in the chancel is from 1450 or so, but there are earlier bits dotted about,” Mr Judd said.
“One of the reasons for upgrading it is because it’s got a combination of medieval past, Georgian additions which are unusual, a Victorian extension and had a huge refurbishment in 1983.
“With the addition of the modern bits of art, all of that together makes it very special.”