Britain has not been immune from political assassination.

Prime Minister Spencer Percevel was shot dead in 1812 as he entered the lobby of the House of Commons on his way to the chamber.

David Hanrahan, increasingly disgruntled at not refused compensation from the Government after being falsely imprisoned in Russia over debt, calmly rose from a chair where he had been warming himself by a fire, produced a pistol from his overcoat and fired it at Percevel, hitting him in the chest. He staggered forward and fell, crying out: "I have been murdered."

More than a century later, could David Lloyd George, the recently appointed Prime Minister in the Great War coalition government, have been next?

MI5 had apparently discovered an audacious plot involving a Southampton husband and wife, her sister and more notoriously her mother in which the the Welsh statesman and Arthur Henderson, the leader of the Labour Party, were to be poisoned with strychnine or curare.

Allegedly none of the four was prepared to carry out the executions but they planned to use a hit man - little suspecting to three of them he was a special agent working undercover who gained their confidence in his assumed role of a conscientious objector, fervently opposed to the First World War and to whom they delivered four phials of the deadly poison.

The key character was Alice Wheeldon who ran a second-hand clothes shop in Derby. Born in 1866, she married her husband William, a commercial traveller, in 1886 and gave birth to a son, also called William, and three daughters, Nellie, Hettie and Winnie.

Daily Echo: Millbrook Road, circa 1900.Millbrook Road, circa 1900. (Image: Echo)

A staunch supporter of the Socialist Labour Party, she was also actively engaged in the Women's Social and Political Union, but at the outbreak of the hostilities she, as a pacifist, fell out with the WSPU who endorsed the campaign. Wheeldon and her daughters also joined the No-Conscription Fellowship and were known to shelter conscientious objectors.

In 1915 Winnie left Derby and moved to Southampton, having married Alfred Mason, a chemist, but she and her brother - who had also moved to the town - continued to be involved in the anti-war movement.

More than three million men had volunteered to serve in the war but it was going badly and with heavy losses being suffered on the western front, the Government introduced conscription which the NCF bitterly opposed and aided conscientious objectors.

So M15 took action by infiltrating the group in the guise of a man called Alex Gordon who sought refuge at Wheeldon's Derby home. A few days later he was joined by Herbert Booth, another supposed conscientious objector and, claiming to be "Comrade Bert", had eluded police on one or two escapades.

They convinced her they could eliminate camp guard dogs enabling conscientious objectors to escape and she agreed with the plan on the condition provided they would help her son - who she claimed had been previously locked up for his political beliefs - flee to America. Mason, she added, would obtain it.

On January 1, 1917, she told the pair it had not arrived but turned a conversation towards the two politicians, saying: "Lloyd George has been the cause of millions of lives being sacrificed. He shall be killed to stop it and as for that other, Henderson, he is a traitor to the people but (Herbert) Asquith is the brains of the business. He has not gone as far as Lloyd George who is neither fit for Heaven nor Hell. Another that should be done is George, of Buckingham Palace. He is always down on people and is no good."

Booth then asked her what was the best way of disposing of the Prime Minister.

Daily Echo: Alfred Mason (left). Spencer Perceval (right).Alfred Mason (left). Spencer Perceval (right). (Image: Echo)

She replied: "We had a plan before and we, the suffragettes, spent £300 in trying to poison him. It was to get a position in a hotel where he stayed and drive a nail through his boot dipped in poison, but he went to France."

When Both asked how the poison was to be administered, she said it was a crystal and he was to put two drops on it, dip the article in and when the water evaporated, it would leave the poison.

Three days later he returned to the house with Gordon to be greeted with a smile from Wheeldon who exclaimed: "We've got it. I got the directions in the letter. Will you copy it?"

Booth did so at her dictation and she then produced a tin tobacco-box containing four glass tubes packed in cotton wool. "I have cleaned all the finger marks off the tubes and the box. Wear gloves when handling them. Now don't forget if you want a microbe, send to me."

Both replied: "I don't think we shall want one."

Wheeldon cautioned: "You never know. Walton Heath will be the best place to catch George with an air gun."

They shook hands and she wished them well. "When you have done them in, you can do the others."

Instead Booth handed over the contents to his bosses and John Webster, a Home Office analyst, confirmed the phials contained strychnine hydrochlorate in powder and solution which would quickly cause convulsions. He added that if half a grain was taken orally or by injection, it could prove fatal.

Daily Echo: Herbert Henry Asquith (left). David Lloyd George (centre). Arthur Henderson (right).Herbert Henry Asquith (left). David Lloyd George (centre). Arthur Henderson (right). (Image: Echo)

The alleged conspirators were also unaware their incoming and outgoing post was being intercepted and photographed.

One letter in particular caught the police's attention, apparently written in part in code, and when Mason's home in Millbrook Road, Southampton was searched, code-linked documents were discovered.

Wheeldon, 50, her daughter Hettie, 27, Mason, 24, and his wife, Winnie, 23, were arrested on January 31.

Mason, the first to be detained, replied after the warrant had been read out to him: "Not guilty" but did admit he had cycled from Southampton to Derby three days earlier, a fact confirmed by his wife when she was taken into custody by Detective Inspector McCormack, of the Southampton Borough force, at Foundry Lane Council School where she worked as a teacher, saying she taught her pupils scripture and morals.

Asked if she had anything to say, she replied: "What is it all about? I don't understand it. My husband has left on his bicycle for Derby. He is a chemist's assistant seeking employment. I know how much I am in it."

The accused appeared before Derby magistrates and in answer to the prosecution's application for them to be remanded in custody, Alice Wheeldon was scathing.

"I think it is a trumped up charge to punish me for my lad being a conscientious objector. You punished me through him while you had him in prison last time. You brought an unfounded charge that he went to prison before and now that he has gone out of the way, you think you will punish him through me and you think you can do it."

Daily Echo: Foundry Lane Council SchoolFoundry Lane Council School (Image: Echo)

Winnine Mason commented: "I think this is an infamous concoction against my family and my husband." Her husband and Hettie Wheeldon did not object.

In addition to the news of the remand hearing, readers of the Hampshire Independent were told Mason had been due to deliver a lecture on pharmacy at the Southampton University College but it was called off after the class had assembled without explanation. He had however informed associates that he was going away but his absence would be brief.

"Mason is an affable man and of ready speech," the paper reported. "Tall and thin, he has a heavy crop of fair hair, clean cut features and a slightly cadaverous expression. He obtained exemption from the Land Tribunal on account of his being a certificated chemist and the grounds of his conscientious objections were not raised.

"His absence was only known to neighbours by the fact that a pianola piano, which was generally playing when he was at home, was silent. He was very fond of music with a good taste for classical compositions. Neighbours say he did a lot of photography at home.

"Mrs Mason had been seen gardening the previous week. She is said to have suffragette sympathies but neither has been seen since."

Curiously their trial, which opened on March 6, was not held in Derby but switched to the Old Bailey.

The prosecution was led by Sir Frederick Smith, the Attorney-General and MP for Liverpool Walton whose department had been responsible for newspaper censorship and pro-war propoganda.

Daily Echo: A prison wardress, Hettie Wheeldon, Winnie Mason and Alice Wheeldon.A prison wardress, Hettie Wheeldon, Winnie Mason and Alice Wheeldon. (Image: Echo)

In his opening speech, he dropped a bombshell when he revealed the evidence would be mainly drawn from the testimony of the two undercover agents but Gordon would not be giving evidence, leading credence to a claim that he had a criminal history and had invented the whole story for money, a fact that his boss, Major William Lee, refused to discuss.

Giving evidence, Alice Wheeldon admitted despising Lloyd George and Henderson and hoped they would be dead as she regarded them as "traitors to the working classes" but was adamant the poison was purely meant for the guard dogs.

Hettie Wheeldon maintained it was Gordon and Booth who suggested they should kill the politicians and she derided the notion of assassination as "ridiculous."

She had been convinced both men were police spies and warned her mother she was being led into a trap: "You can do what you like but I am having nothing to do with it."

Winnie Mason followed the same line as her mother of the poison target, and her husband insisted: "I would not have supplied strychnine to kill a man as is too bitter and easily dectected by the intended victim," adding that curare would not kill anything bigger than a dog.

Saiyid Haiden Riza, selected by Alice Wheeldon as defence counsel because of his socialist leanings, told jurors the height of the evidence was based on the words and actions of an absent witness and demanded the prosecution to produce him in the public interest so that he might be cross-examined.

"If this method of the prosecution goes unchallenged, it augurs ill for England."

Daily Echo: Southampton University CollegeSouthampton University College (Image: Echo)

However in his summing up, the judge, Mr Justice Low, virtually overruled him by declaring that without the use of enemy agents it would be impossible to detect such crimes. However he agreed that if they rejected Booth's evidence, the case against them to a large extent failed.

In fact they didn't and within half an hour convicted Alice Wheeldon, her daughter Winnie and her son-in-law.

Alice Wheeldon received ten years, Alfred Mason seven and Winnie five. Her sister was acquitted.

But not everyone was convinced the truth came out, with fresh calls for Gordon to give evidence in a re-trial and Basil Thompson, Deputy Commissioner for Metropolitan Police, conspicuously savaged it as a case of entrapment by "putting the idea into the woman's head, or, if it was already there, by offering to act as a dart thrower."

Alice Wheeldon adopted a policy of non-cooperation with prison authorities and as her condition worsened in Holloway, Lloyd George was warned that it would be "very undesirable" for her to die behind bars. He took the advice and she was released on New Years Eve, Wheeldon acknowledging her gratitude. "It was very magnanimous of him. He has proved himself to be a man."

That intensified the campaign for Mason and his wife to be similarly treated and they were duly freed in January 1919.

But mother and daughter were not united for long. Alice Wheeldon apparently never recovered from her time in custody and died the following month from the pandemic flu.

Descendants of the Wheeldon family have since vowed to clear their names.