<P> With the publication of F. W. Winterbotham's The Ultra Secret (1974) public discussion of Bletchley's work finally became possible (though even today some former staff still consider themselves bound to silence) and in July 2009 the British government announced that Bletchley personnel would be recognised with a commemorative badge . </P> <P> After the war, the site passed through a succession of hands and saw a number of uses, including as a teacher - training college and local GPO headquarters . By 1991, the site was nearly empty and the buildings were at risk of demolition for redevelopment . </P> <P> In February 1992, the Milton Keynes Borough Council declared most of the Park a conservation area, and the Bletchley Park Trust was formed to maintain the site as a museum . The site opened to visitors in 1993, and was formally inaugurated by HRH The Duke of Kent as Chief Patron in July 1994 . In 1999 the land owners, the Property Advisors to the Civil Estate and BT, granted a lease the Trust giving the Trust control over most of the site . </P> <P> June 2014 saw the completion of an £ 8 million restoration project, which was marked by a visit from Catherine, Duchess of Cambridge . The Duchess' paternal grandmother, Valerie, and Valerie's twin sister, Mary (née Glassborow), both worked at Bletchley Park during the war . The twin sisters worked as Foreign Office Civilians in Hut 6, where they managed the interception of enemy and neutral diplomatic signals for decryption . Valerie married Catherine's grandfather, Captain Peter Middleton . </P>

When did bletchley park open to the public