Calla looking flowers in "the queen" when she walks with the queen mother in the garden?

Question

they are tall and white looking and are along a wall in the garden in the movie

Answer 1

It is a long perennial bed of "red hot pokers" (kniphofia). They are also known as torch lilies. If you look at the movie you will see that the flowers are mostly cream with orange at the top. They were popular perennials in Victorian times in the UK.