The answer is definitely Vanessa Redgrave, who was allowed to enter the U.S. Embassy in London, with 3 supporters, to deliver a protest against the Vietnam War on 17 March 1968, after she had spoken at the Rally in Trafalgar Square, but before events on the day turned nasty and violent.
Hanoi Jane is/was a name given to Jane Fonda, when, in 1972, she travelled to North Vietnam and made 4 broadcasts on North Vietnamese radio, criticising American policy and administration.
keyboardix- I think you have taken my answer the wrong way. I knew the answer was Vanessa Redgrave, my response was to the answer immediately before mine which mistakenly gave her the nickname "Hanoi Jane".