SLASHER Mary waited for her moment, quietly sketching away like many other visitors in the National Gallery in London.

Her eyes, though, were more on the guards than they were on the details of the world’s most famous paintings on the walls.

One guard, she noted, had gone for his lunch. Then she saw the other pick up his newspaper so that it obscured his view of her movements.

This was her moment. She slid a small meat clever out of her sleeve, and jumped into action, attacking the most famous bottom in the world.

Her first blow broke the “anti-suffragette glass” that had been placed protectively around the delicate derriere of the Rokeby Venus – a much admired nude named after the Teesdale mansion in which it had hung for a century.

The newspaper-reading guard heard the blow but, even though he was aware that there were rumours of a suffragette attack, he glanced up at the ceiling, thinking that was from where the sound emanated.

This gave “Slasher Mary” a few precious seconds to inflict seven deep wounds on the back of Venus.

“Directly she produced the hatchet, the woman flung herself at the picture,” reported The Northern Echo’s front page on March 11, 1914. “She shivered the glass with a sturdy blow, and then hacked at the canvas with as much force as if chopping a block of wood.”

The plain clothes detectives and guards then pounced on 31-year-old Mary Richardson, a regularly arrested suffragette, and a taxi was hailed to cart her off to Holloway jail – the prison where many suffragettes, including Mary, had been incarcerated as their campaign to get women the vote had turned violent.

Just the day before the outrage, Emmeline Pankhurst, the leader of the radical Women’s Social & Political Union, had been arrested.

“It would appear that the Union was aware of Miss Richardson’s intentions,” said the Echo, “for she had written and signed a statement explaining her act before she started for the National Gallery.”

The Echo then reproduced the statement: “I have tried to destroy the picture of the most beautiful woman in mythological history as a protest against the Government for destroying Mrs Pankhurst, who is the most beautiful character in modern history.

“Justice is an element of beauty as much as colour and outline on canvas. Mrs Pankhurst seeks to procure justice for womanhood, and for this she is being slowly murdered by a Government of Iscariot politicians.

“If there is an outcry against my deed, let everyone remember that such an outcry is a hypocrisy so long as they allow the destruction of Mrs Pankhurst and other beautiful living women, and that until the public cease to countenance human destruction, the stones cast against me for the destruction of this picture are each an evidence against them of artistic as well as moral and political humbug and hypocrisy.”

In later life, Mary also explained that she didn’t like the way men gawped at the naked beauty all day long.

Beneath the Echo’s report of the outrage, the paper told how the Venus came to be associated with a corner of Teesdale.

The Toilet of Venus, to give it its proper title, was painted in about 1658 by Diego Velazquez, the leading painter of the Spanish Golden Age. It shows the sensuous curves of the naked back of Venus reclining on a bed, but Cupid, the Roman god of physical love, is holding a mirror which is angled to allow the viewer to see the enigmatic face of Venus.

Art critics say that the face in the mirror is much older than the shapely bottom would suggest, thus providing a warning about the passing of time and the inevitability of aging.

In Catholic Spain, such nudes were rare, and the kings kept the painting for their private enjoyment until 1802 when Charles IV gave it to a favoured minister. In 1809, the painting was bought by John Bacon Sawrey Morritt, “a distinguished lover of art”, who lived at Rokeby, a huge mansion near Greta Bridge on the A66.

“The Venus was placed at first in Mr Morritt’s town house in Portland Place, London, where he was visited by Sir Walter Scott, Sir Joshua Reynolds, Sir Thomas Lawrence, and Sir Humphrey Davy,” said the Echo.

“When Mr Morritt died, the Venus was removed from London to Rokeby, where it remained so long that it became known in art circles as the ‘Rokeby Venus’.”

It hung there until the Morritts needed to liquidate it in 1905, in jingoistic days when Germany was trying to buy up the world’s leading artworks. The Rokeby Venus, though, became the first painting to be purchased by the newly-formed Art Fund charity, which presented it back to the British nation and so it was hung in the National Gallery where Slasher Mary discovered it.

It cost the nation £45,000 – about £5.2m in today’s values – although, due to agent’s fees, the Morritts only received £25,000 (a mere £2.9m).

The loss of the Rokeby Venus must have left a dusty mark over the fireplace because the Morritts then commissioned a copy of it. In the Second World War, the mansion was used as a military convalescent home and the copy of the famous bottom was taken to the officers’ mess at RAF Leeming. During an exuberant party, the poor Venus sustained a bullet wound to the bum.

She was patched up, and the copy remains in Rokeby, just as the original was patched up after Slasher Mary’s attack, and it can still be seen in the National Gallery.

RECENT MEMORIES have told how the original manor house at Rokeby was burned to the ground in 1343 by rampaging Scots, and its owners built a fortified peel tower “two bow-shots” away so they could keep an eye out for any future hostile incursions. This haunted peel tower, called Mortham Tower, is owned by a member of the Morrison supermarket family and is now on the market for about £3m.

In the 1720s, Mortham Tower became the home of the Sir Thomas Robinson, a man of extravagant tastes in everything from architecture to parties. He spent a decade, from 1725 to 1735, building a magnificent Palladian mansion on the site of the burned out manor house.

An amateur, but talented, architect, Sir Thomas was very hands on during the construction of Rokeby, which cost him so much that he had to accept a job as the governor of Barbados to cover the bills. But in Barbados, he extravagantly built himself an arsenal and, with his generous hospitality also draining his bank account, he was forced to sell Rokeby in 1769 to John Sawrey Morritt. It was JS Morritt’s son, JBS Morritt, who bought the Venus.

HOW do you pronounce “Rokeby”? Today, it seems that most people say “Row-kby” but in ancient times it was “Rook-by”, because it was a settlement surrounded by rooks. Caw!

However you pronounce it, Rokeby is still owned by the Morritt family, and it is open to the public on Mondays and Tuesdays each week until September 5, from 2pm to 5pm. Admission for adults is £8, although concessions are available.

The other aspect of this story is its connection to the suffragettes. By 1914, the terrorist-like violence of their methods was alienating many moderate people. When war broke out, they put their violence aside, and in 1918, the first women were allowed the vote.