Which woman should go on a banknote next?

Since it was announced that Bank of England banknotes would soon only feature famous men, a campaign has been gathering steam. Which woman should be next?

Somewhere on Threadneedle Street, a woman's face appears drawn on to a banknote.

The face is not that of social reformer Elizabeth Fry, whose glowering visage has graced the Bank of England's £5 note for more than a decade.

And she could hardly be confused with Sir Winston Churchill - the man named as Fry's successor. Although the bank confirms her existence, it will not share her name.

The woman has been chosen as a "contingency candidate", ready to move into production at a moment's notice should the Churchillian note be compromised by a spike in counterfeiting, or some other peril.

Her selection as a mere back-up has done little to assuage the concerns of those angry at the Churchill decision. It is not that they disagree with Churchill but that they are shocked that, apart from the Queen, soon no famous woman will be on a Bank of England note.

It's goodbye to Elizabeth...

Now campaigners want to find out what goes on in the bank's selection process. A group of 46 MPs have written to the bank to ask them to reconsider their decision to get rid of Fry and not replace her with another woman.

Caroline Criado-Perez, co-founder of The Women's Room, a group fighting to end the opaque selection procedure, thinks that the bank's secrecy may even be illegal.

The Equality Act requires all public institutions to try and eliminate discrimination. But without explaining how Churchill won the contest, she says, we can't know if the bank has acted within the law.

And hello to Sir Winston

"At the moment it's hard to argue that the process isn't discriminatory," she says.

The bank says its requirements are quite clear, though, and that candidates must meet four key criteria to be eligible for selection.

They must have made a lasting contribution to society, have a widely recognised name, not be controversial, and there must be good artwork on which a design can be based.

Judging by former cases, however, the rules have not always been applied consistently.

Fry herself was not widely known prior to her selection, and knowledge of Sir John Houblon - the former Bank of England governor currently on the reverse of £50 notes - was arguably mainly restricted to hardcore pub quizzers and bank employees.

The historian Judith Flanders points out that good artwork was not available for all those who have made the cut. "We have no idea what William Shakespeare looked like," she says.

Indeed, the playwright that featured on the £20 note through the 70s and 80s bears little resemblance to Martin Droeshout's famous copper engraving that we most readily associate with the Bard.

Flanders thinks the long list of men offered a place on Britain's banknotes reflects a form of prejudice.

"It's about white upper class men from limited backgrounds having a limited number of heroes. What is this except a public school boy's list?"

She suggests a long list of women who could be feature on the note - suffragette Emily Davison, National Trust founder Octavia Hill and novelist George Eliot to name just a few.

MP Stella Creasy has been leading a campaign on the issue in Westminster, and has co-written a letter to the bank, along with 45 other MPs.

The letter suggests four more women as potential candidates. Mary Seacole, who created a hotel to aid wounded soldiers during the Crimean war, women's rights advocate Mary Wollstonecraft, biophysicist Rosalind Franklin, who contributed to the discovery of DNA, and another suffragette Emmeline Pankhurst.

"Nobody's suggesting that Winston Churchill doesn't deserve to be on the note. We're simply saying that if women aren't represented, it suggests that they don't make a contribution to society," says Creasy.

"All of these little things add up to much bigger things, which is why we think the bank should review its decision.

Mary Wollstonecraft graffiti adorns London's Newington Green Unitarian Chapel

"In Australia there is a 50/50 split, and in Israel, Norway, Denmark and Scotland women are better represented."

Dawn Bonfield of the Women's Engineering Society has also written to the bank's Court of Directors naming three scientists as contenders. Electrical engineer Caroline Haslett, aviator Amy Johnson, and mathematician Ada Lovelace - considered by some the world's first computer programmer - should all be considered, she says.

"The work that women do is being ignored and sidelined. Why have the same white man as usual? Do we want to tell the same stories all the time?" she says.

Bonfield thinks that representation on banknotes is of particular importance. "We need something that you see everyday. It's there without you even noticing - so it's an underlying reinforcement."

Elsewhere in the UK, there are famous women on banknotes. In Scotland, where retail banks can issue notes, the Clydesdale Bank has doctor and suffragette Elsie Inglis on its £50 notes and missionary Mary Slessor on one of its £10 notes.

Incoming Bank of England governor Mark Carney is set to feel the force of the protest when he steps into his new job on 1 July.

Criado-Perez plans to present him with a petition with almost 25,000 signatories and has raised nearly £12,000 to take the institution to court over the issue.

"They're doing whatever they can not to make the decision making process clear," she says. "I'm just asking them to abide by the law."

The bank says it welcomes public involvement, and publishes the suggestions sent in by those keen to participate. Arranged chronologically they stretch from Queen Boadicea and Lady Godiva at one end to Katie Price and Jonny Wilkinson at the other.

When it comes to the final decision, however, the institution is currently standing firm. "This is a matter to be determined by the bank," it stated, in response to a Freedom of Information request.

The future of the note is not yet certain. If it does remain unchanged, however, a spike in counterfeiting appears to the campaigners' best hope.

Here is a selection of your nominations, from crime author Agatha Christie to Victorian era surgeon Elizabeth Garrett Anderson and WWII spy Violette Szabo - and Mervyn King's musings on Jane Austen as a candidate.