It was 9am one day in mid-July when the cotton hood fell over her face and Ruth Ellis, the last woman to be executed in Britain.

Now, 52 years after the hanging at Holloway Prison, an author in Bookham believes she has uncovered evidence that exonerates the condemned nightclub hostess.

Monica Weller spent five years researching the circumstances that led Ellis, 28, to shoot dead her lover, David Blakeley, outside a pub on Easter Sunday in 1955.

Her findings, highlighting discrepancies in documentary evidence, have prompted Prime Minister Gordon Brown to agree to post her petition to re-open the case on the Downing Street website.

Mrs Weller, 57, said: "I just want to be able to tell the British public the truth after half a century of spin. The hope is that Mr Brown uses his influence to recommend Her Majesty to grant a free pardon."

Ellis shot Blakeley, a racing driver with whom she was having an affair, outside the Magdala Tavern in north London.

No defence of any substance was put at her trial and the jury was prevented from returning a verdict of manslaughter on the ground of provocation.

This week Mrs Weller said there was a miscarriage of justice because Ellis was unable to fire the .38 Smith and Wesson revolver, which is operated with two hands.

While researching a book with Ellis's sister, Muriel Jakubait, she discovered the hanged woman's left hand was gnarled by rheumatic fever.

It also emerged no ballistic tests were done because the gun "broke" at the Metropolitan Police laboratory, and that Ellis's light clothes were spotless as she was escorted from the bloody crime scene.

Mrs Weller said: "I have presented a range of evidence the court never got to hear; evidence pointing to the fact that Ruth Ellis was innocent of the crime she was hanged for."

Go to petitions.pm.gov.uk/RuthEllis55/