"You see I think that early on, when she became Queen, I think that she had to sacrifice within herself an awful lot of emotions and thoughts of the future and everything else. But I think with horses it's another world in that it reduces you to just the person in relation to the animal, and you're not a Queen, you're just a human being," Margaret Rhodes tells a BBC documentary to aired here on Monday.
Her first reported riding lesson took place in the private riding school at Buckingham Palace Mews in January 1930, when she was still only three years old.
Last month, she spent her 87th birthday at the yard of a West Country trainer casting an eye over horses.
The programme features commentary by the Queen's staff, past and present, involved with the training and welfare of her horses and ponies which number around 180 and are kept at various royal residences and stables from Sandringham to Balmoral.
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The Princess Royal, the Queen's daughter Anne, in her contribution to the documentary speaks about how horses were always a part of her life.
The documentary features extensive footage of the Queen with her horses.
She is shown inspecting new foals soon after they are born and others that are a year old.
Apart from horses, the Queen also has had a lifelong love of dogs, especially her Pembroke Welsh Corgis.