Black & white photos: University of Tennessee, Special Collections Library
Archaeology students from Bristol University are digging deep in an attempt to unravel the mystery of Tyntesfield's hidden wartime history.
The annual summer dig aims to uncover more about what is thought to be the site of a World War II American army camp at the top of the estate.
It is even rumoured that Tyntesfield's lake was emptied to avoid catching the attention of enemy aircraft.
The dig is open to visitors and runs until Wednesday, 26 August 2009.
Estate staff say there is strong evidence that Tyntesfield was used extensively during WWII and it is thought that the army camp site, which shows a collection of building foundations and doorways, is part of the estate's hidden wartime history.
Katie Laidlaw, who is running the summer dig, said: "Thanks to local people and archived records we know that during the war Tyntesfield was home to one of the largest American Army Hospitals in Europe.
"Girls from Clifton High School were evacuated to the house to sleep away from the threat of bombings in Bristol.
"We're fairly sure that this site is part of the picture too but we know very little about it so we are keen to find out more."
The National Trust at Tyntesfield would love to hear from anyone who thinks they can help solve this wartime mystery or has any memories of Tyntesfield during WWII.