The history books will have to be rewritten following a major discovery about one of Sheffield's oldest places.
Bishops' House, a Grade II* listed timber-framed Tudor building on Norton Lees Lane, gained its name as it was believed to have been built for two senior priests in the 1500s.
However, tests have revealed that the oldest part of the house dates from 1554, more than 50 years later than previously thought - meaning the bishops could never have resided there.
Nick Roscoe, chair of the Friends of Bishops' House, said: "The earlier histories have been turned on their head."
The site, at the southern tip of Meersbrook Park, is owned and maintained by Sheffield Council, but the Friends group has kept the attraction open to the public after volunteers fended off the threat of closure in 2011.
The society commissioned a tree ring dating study - analysing the natural growth marks in the house's wooden structure - to determine when exactly the property was built.
Ken Dash, a local historian and group trustee, said: "Tree ring analysis was first done when the house was restored in the 1970s, and this suggested that it was built around 1500. Techniques have moved on though, and when we got the results back they were accurate to the year, and very surprising.
"The oldest part of the house was actually built in 1554. This is more recent than we thought and was not what we expected."
Ken, who has been surveying and researching the building for five years, said the more precise date laid to rest a rumour started in the Victorian era that gave rise to its name. The tale was inspired by two brothers, John and Geoffrey Blythe, who lived locally, became bishops and were ancestors of the family that owned the house.
"For Bishops' House to have been their house it would've needed to have been built much earlier. Perhaps there was an earlier house on the site which they lived in, we do not know."
The study has also shed fresh light on the timeline of the building's construction, Ken added.
"We always assumed the house was built in two stages, but it turns out the research passed down from 1976 had the order wrong. What we had thought was the extension turns out to be the oldest part of the house. The bigger part of the house, including the main hall, was actually built 26 years later in 1580, not earlier as the original research found.”
Nick said: "It’s thanks to Ken’s hard work that we have got this far. He studied the timbers carefully and suspected there was something amiss with the previous dating, so we decided we had to investigate further."
He admitted: "Our guidebook and guided tours will have to be rewritten - but it’s exciting to really enhance our knowledge of the building."
A team of more than 30 volunteers runs the house, hosting events ranging from free history talks to children’s craft sessions, medieval fairs, poetry readings and live music. School visits are a regular fixture and the house is licensed for weddings.
New helpers are needed to keep the site open at weekends, and to fill other roles. Email email@example.com for details - no experience is needed.
As part of the annual Heritage Open Days festival in Sheffield, Robert Howard, an expert from the Nottingham Tree Ring Dating Laboratory, was at Bishops' House last Sunday, and gave a short talk.