© Jordan Strauss/Invision/AP Helena Bonham Carter arrives at the 26th annual Screen Actors Guild Awards at the Shrine Auditorium & Expo Hall on Sunday, Jan. 19, 2020, in Los Angeles. (Photo by Jordan Strauss/Invision/AP) The Crown star Helena Bonham Carter is marking the bicentenary of Florence Nightingale's birth by urging the public to buy a symbolic white rose.