Wanamaker told friends he wanted to stay in Britain with his family because of its tolerance towards Communism -- and appeared to have no idea he was under surveillance by the domestic intelligence agency MI5.
His daughter Zoe Wanamaker is now one of Britain's best loved actresses. She starred in "Harry Potter and the Philosopher's Stone" as Madam Hooch, the teacher who taught the boy wizard to fly a broomstick.
As Cold War fever swept the West, MI5 identified Wanamaker as soon as he arrived in Britain in 1951 from the United States, where had been due to give evidence to the US Senate committee investigating communist activity.
The files show his conversations, associations and even his theatre projects were recorded and passed on to the US embassy.
"He continues to maintain contact with what are generally regarded as left-wing theatrical groups," MI5 wrote in September 1952.
"The general impression prevailing in the theatrical world is that Wanamaker appears very sympathetic towards communists and communism."
Wanaker, who later led the project to rebuild Shakespeare's Globe Theatre in London, was apparently unaware of the interest in his life.
He was reported as saying in February 1955 that "the British tolerance towards Communism was in the true spirit of modern democracy and as he appreciated the British way of life he intended to apply for permanent residence in the UK in order to bring up his children here".
In the same document, MI5 noted that in the event of a national emergency, Wanamaker should be interned and his wife's movements restricted.
The family were forced to apply for repeated extensions to their permit to stay in Britain, and it was not until 1957 that MI5 accepted that despite his political views, Wanamaker was determined to keep out of trouble.
In March 1957 the family was granted indefinite leave to remain -- although MI5 continued to keep tabs on their activities for many years afterwards.
Wanamaker starred in Shakespeare plays on both sides of the Atlantic, acted and directed in numerous films and in 1970 founded the Shakespeare Globe Trust to work towards re-creating the famous Globe Theatre.
He saw construction begin at the site but died in 1993, four years before it was finally opened.
Source: AFP Global Edition