Elizabeth Woodville, queen consort of King Edward IV of England and the narrator of Philippa Gregory's historical novel The White Queen, first describes Richard—who was then Duke of Gloucester, later to become King Richard III—at a Twelfth Night celebration at Christmastime in 1469.
The youngest York brother, Richard, Duke of Gloucester, now seventeen and a handsome slight boy, may be the baby of the family, but he has never been the favorite. Of all the York boys he is the only one to resemble his father, and he is dark and small-boned, a little changeling beside the big-boned, handsome York line.
Elizabeth doesn't say much more about him physically, except to mention his general hair color two years later, on the occasion of her husband's triumphant return to England from his victories in France.
I see Richard’s dark head far below me, at the old king’s doorway, as if he is waiting to enter; and I hear George’s voice floating up the stairwell. “We thought you had changed your mind!”
Elizabeth description bears no resemblance whatsoever to Richard's description of himself in Shakespeare's Richard III.
GLOUCESTER. ... I, that am rudely stamp'd, and want love's majesty
To strut before a wanton ambling nymph;
I, that am curtail'd of this fair proportion,
Cheated of feature by dissembling nature,
Deform'd, unfinish'd, sent before my time
Into this breathing world scarce half made up,
And that so lamely and unfashionable
That dogs bark at me as I halt by them ... (Rich. III, 1.1.16-24)
In act 3, scene 4, Richard says that he's been bewitched—by none other than the White Queen herself and King Edward IV's mistress, Jane Shore—and offers his withered arm as proof of their witchcraft.
GLOUCESTER. Then be your eyes the witness of this ill:
See how I am bewitch'd; behold mine arm
Is, like a blasted sapling, wither'd up:
And this is Edward's wife, that monstrous witch,
Consorted with that harlot strumpet Shore,
That by their witchcraft thus have marked me ... (Rich. III, 3.4.69-73)
Elsewhere in the play, Richard is described by Queen Margaret as a "poisonous bunch-backed toad" (Rich. III, 1.3.260), emphasizing Richard's hunched back.
Richard describes his deformities more specifically in Shakespeare's Henry VI, Part 3:
GLOUCESTER. Why, Love forswore me in my mother’s womb,
And, for I should not deal in her soft laws,
She did corrupt frail Nature with some bribe
To shrink mine arm up like a withered shrub;
To make an envious mountain on my back,
Where sits Deformity to mock my body;
To shape my legs of an unequal size;
To disproportion me in every part ...(3 Henry VI, 3.2.155-162)
In all, Shakespeare's Richard III—the Richard III that has come down to us through the ages—suffered from a withered arm and a hunched back, had one shoulder lower than the other, and walked with a limp, because one of his legs was shorter than the other.
An interesting aspect of the physical description of Richard is that The White Queen was first published in August of 2009, and it was in 2012 that archaeologist discovered a skeleton buried beneath a parking lot in Leicester—near the site of an old monastery located not far from Bosworth Field, where Richard III was killed in battle. In 2013, the skeleton was confirmed by DNA to be that of Richard III.
Study of the skeleton revealed that Richard suffered from scoliosis, a curvature of the spine. Although Richard might not have had the other traditional deformities—withered arm, one leg shorter than the other—his scoliosis might appear to Richard's contemporaries as a hunched back, and this disease would likely have caused one of his shoulders (the right one) to appear higher than the other.
However, Elizabeth Woodville's description of Richard as he appeared at Twelfth Night in 1469 might well be factually correct. Scoliosis is a disease which usually develops in adolescents between the ages of ten and eighteen. When Elizabeth first described him at age seventeen, Richard might simply have not yet been showing any signs of the disease.
As a side note, the ten-part BBC television series The White Queen premiered in June, 2013, just a few months after Richard's skeleton was confirmed by DNA.
Even if the producers of the television series had wanted to be historically accurate regarding Richard's scoliosis, the production of the series was already well underway, and it would have been logistically impossible and financially prohibitive to change Richard's physical appearance at that late date in the production schedule. They would simply have to make do with handsome Welsh actor Aneurin Barnard in the role of Richard III.