A story some may not know, its hundredth anniversary set for June 2013.

An accidental martyr? The 100-year mystery of why suffragette Emily Davison threw herself under the king's horse (Sunday Mail)
Racehorses are galloping at full speed around Tattenham Corner in the Epsom Derby. This is the last bend before the final straight and the winning post, where thousands of racegoers are cheering in the stands, and King George V and Queen Mary are watching from the Royal Box. There is a roar from the crowds as the horses round the long left turn. Then a woman ducks under the railings and runs on to the racecourse.

In an instant, she is knocked flying (and) lies on the turf, more like a heap of rags than a person. The crowd, who a moment before had been cheering, surges towards the turf and surrounds the prone figures. The time is 3.10pm, 4 June 1913. It will be remembered as the moment when a suffragette ‘threw herself under the King’s horse’.

The iconic image of the suffragette being trampled by George V’s horse has come to symbolise the bitter struggle that women fought to win the right to vote in Britain. The arguments about what actually happened that day have continued ever since.

The woman at the Derby is Emily Wilding Davison, a leading militant in the Women’s Social and Political Union (WSPU), founded in 1903. Four days later, Emily dies in hospital of her injuries without regaining consciousness. She is 40. But the archive footage of Emily’s protest does not answer the nagging question: did she mean to commit suicide at the Derby?

Her protest was just the latest in a series of militant outrages that appalled polite Edwardian society. Parliament and the press were united in their conviction that Emily had crossed a line: this was no longer justified protest but ‘wicked madness’.
Emily Davison died on 8 June without regaining consciousness.
The police and government clearly preferred the fiction that Davison was a mad woman, intent on a reckless act of martyrdom, and chose the King’s horse by accident. They did not want the public to hear that the true target of her shocking protest for women’s suffrage had been the monarchy. Any attack on the King (or his horse) was not only unthinkable, it was seditious.
The coffin was taken to King’s Cross station and then put into a goods van for its final journey to Morpeth in Northumberland. Huge crowds turned out the next day in Morpeth as Emily was buried in the family grave. The site is marked by a large stone monument with a cross on top and the suffragette slogan ‘Deeds not Words’.
much more, including pictures and a video of the incident, at link above

from Real Britannia: Our Ten Proudest Years, the Glory and the Spin by Colin Brown