COWBRIDGE House in Malmesbury, where radar was developed during the Second World War, will be on view for the last time later this month.
The house, incorporated into the former Lucent Technologies site on the Swindon Road, was bought by property leasing firm, the Minton Group, for an undisclosed sum last year.
The company has yet to get permission to build 155 houses on the land but has said Cowbridge House will be demolished as part of the scheme.
It has allowed a last public viewing on January 31 before the bulldozers roll in.
The building, once a large country house and estate, was bought in 1939 by Southend firm E K Cole, known as ECKO, which conducted secret tests to develop radar during the war.
The building is very different and over the years there have been a number of extensions. The Minton Group said it could not be used in the new plan.
However, it said some of the fittings may be salvaged including the staircase and stained glass windows.
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