During the second world war, the government fought a secret campaign against German spies. Now, new letters from the MI5 archive reveal the true story of Jose Waldberg, one of the men who was executed

Early on the morning of Tuesday 3 September 1940, two single-masted French fishing boats, La Mascotte and the Rose du Carmel, slipped across the Channel and approached the coast of Kent. When they were a few hundred yards from the headland of Dungeness, four men clambered from the vessels into a pair of rowing boats, and made their way silently to shore.

The four were Carl Meier, 23, a Dutch-born Nazi party member who had spent a little time in Birmingham before the war; Charles van den Kieboom, 25, a Dutch-Japanese dual national; Sjoerd Pons, 28, a Dutchman; and a 25-year-old who described himself as German and called himself Jose Waldberg.

They were agents of the Abwehr, the German military intelligence service, and their mission was to reconnoitre England’s south coast for the invasion they had been led to believe was just weeks away. Their supplies of corned beef, baked beans and chocolate were to last for around 10 days, and the small radio transmitters they had brought with them contained valves that quickly burned out.

Officially, they were part of Operation Lena, the codename for the Abwehr’s contribution to Hitler’s invasion plan. Unofficially, their spymasters considered their mission to be so hazardous that they called it the Himmelfahrt: the ascension to heaven.

Just 13 days after Winston Churchill came to power, the Treachery Act became law. It carried only one sentence: death

The tale of what happened to these men has been told before. But one sad and salient element of their story has remained hidden, buried for years in the archives of MI5 in poignant letters that have only now come to light after being transferred to the UK National Archives at Kew, south-west London.

Meier was the first to be captured, after he walked the short distance to the village of Lydd and strolled into the Rising Sun pub to ask landlady Mabel Cole for a bottle of cider. Cole was immediately wary of this young man with a foreign accent, who was unaware that he could not buy alcohol in a British pub at 9am. She was even more suspicious when Meier struck his head on the pub’s traditional low ceiling as he walked out. The police were called, and within hours all four would-be spies had been rounded up.

During six weeks at MI5’s interrogation centre, Camp 020, at Ham, in the south-western suburbs of London, all four were persuaded to make lengthy statements. On 24 October, they were charged under the Treachery Act, brought before magistrates at Bow Street court under conditions of complete secrecy, and told they would stand trial at the Old Bailey the following month.

To describe the Treachery Act as having been rushed on to the statute books would be an understatement.

When Churchill entered Downing Street on 10 May that year, he could not accept that the Germans’ rapid victories across Norway and western Europe could be attributed solely to superior weaponry, tactics and fighting spirit; there must, he concluded, be fifth columnists at work behind the lines. He was also convinced that fifth columnists must be at work in Britain, and wanted them rooted out and destroyed. On being told that any British nationals among them could be prosecuted for treason, but that foreigners probably could not, the new prime minister demanded a new law – immediately.

Winston Churchill in Downing Street, 1941. Photograph: Planet News Archive/SSPL via Getty Images

By 23 May, the Treachery Act, which outlawed conduct “designed or likely to give assistance to the naval, military or air operations of the enemy” had passed through parliament and received royal assent. It carried only one sentence: death.

When the trial of the four spies opened on 19 November, the prosecution asked the judge to make an order under the Emergency Powers (Defence) Act banning “disclosure of any information with regard to any part of the proceedings”. By lunchtime, reporters supping in the Bell Tavern, 200 yards from the Old Bailey, in Fleet Street, were aware that something was afoot in court one, but could not get in. They also knew that they would not get any story past the censors at the Ministry of Information.

Waldberg surprised the court by pleading guilty. Meier, Kieboom and Pons denied the offence. Pons told the court that he had assisted the Abwehr under duress: he had been threatened with incarceration in a concentration camp after being caught smuggling gems from Holland to Germany, and insisted he had no intention of doing anything to assist the Germans on arrival in England.

After a trial that lasted four days, the jury took less than 90 minutes to convict Meier and Kieboom, who were sentenced to death, along with Waldberg. The jury accepted Pons’s defence, however. He was acquitted, set free, and immediately detained once more as an enemy alien.

In due course, Waldberg and Meier were informed that they were to be hanged at Pentonville prison in north London at 9am on 10 December. Kieboom was to hang a week later. Still, not a word about the case had appeared in the press or been uttered by the BBC.

Charles van den Kieboom, who was hanged as a German spy.

A week before the first executions, Sir Alexander Maxwell, the donnish permanent under-secretary at the Home Office, began having serious misgivings about the way in which the three men had been prosecuted and sentenced to death in complete secrecy. He set out his concerns in a confidential letter to Viscount Swinton, the head of the Security Executive, a body established by Churchill to manage MI5, and to root out the supposed fifth columnists. “Public opinion and public criticism is the most important safeguard for the proper administration of justice,” he wrote. “To carry out sentences of this kind in secrecy is contrary to all our traditions.”

Not that Maxwell was going to suggest that any future spy trials should be open to the press and public; rather, he wanted to be sure that if such secrecy were to be the cause of any future problems, it would be Swinton and MI5 that would take the blame, and not the Home Office and his boss Herbert Morrison, the home secretary. “The home secretary … may at any time be asked by his colleagues or perhaps by the Lord Chief Justice whether he is satisfied that these unusual steps are really necessary in the interests of the defence of the realm,” he explained to Swinton. “I think he ought to have on the Home Office records a letter from you on the subject. The home secretary should be safeguarded by a full statement from the Security Service.”

Swinton’s reply two days later explained that some enemy agents had already been “turned” by MI5, and played back against their Abwehr masters. Those whose capture members of the public had witnessed – or who refused to play the game – would be prosecuted under the Treachery Act.

In time, this deception operation, known as Double Cross, would be seen as one of MI5’s greatest achievements, and it would become a vital part of the allied strategic deception that also relied heavily on the code-breaking efforts of Bletchley Park. Agents who were turned would send their Abwehr handlers a careful blend of correct and incorrect intelligence. They would also ask for reinforcements, with new code books and radios, and plenty of cash, and these men would also be captured. Before long, German intelligence was unwittingly financing the Double Cross operation that was being directed against it. So great a failure was Operation Lena that one historian has recently concluded that anti-Nazis among the upper reaches of the Abwehr must have sabotaged it.

Swinton explained to Maxwell that Double Cross was vital to the war effort. “The combined work of all the services has built up, and is continually adding to, a great structure of intelligence and counter-espionage. A single disclosure, affecting one individual, might send the whole building toppling. Even in passing sentence, a judge may inadvertently err.”

By the time Maxwell had received Swinton’s explanation, however, it was becoming clear to both the Home Office and MI5 that there was a serious problem with one of the secret convictions. At Pentonville, Waldberg was insisting his name was not Jose Waldberg at all, and that he was not German. His name, he insisted, was Henri Lassudry, and he was Belgian.

Initially, MI5 was inclined to brush aside these claims as the desperate fabrications of a condemned man. The agency’s records show, however, that when interrogating Waldberg about his claims, a French-speaking interpreter was used, as the prisoner’s French was excellent – “like a native speaker” – while his German was weak. Furthermore, when “Waldberg” was given the chance to write a number of final letters to his family, he wrote to his parents, a Mons & Mme Lassudry, at an address in Rue des Colonies, Brussels, and a girlfriend, Helene Ceuppens, in nearby Ixelles.

These letters contain an explanation for the plea that had so surprised the Old Bailey. Lassudry complained that his barrister, a man called Blundell, had advised him to enter a guilty plea, without informing him that he would be sentenced to death as a consequence. Lassudry thought he would have a chance to explain himself to the judge. Had he done so, he would have entered the same defence that had saved Pons from the gallows. He was acting under duress, having been a prisoner of the Gestapo, who threatened to arrest his father if he did not agree to undertake the spying mission to England.

Facebook Twitter Pinterest A letter relating to the case of Henri Lassudry, AKA Jose Waldberg. Photograph: National Archives in Kew

In the event, he had no chance to speak to the judge, and his sentencing hearing lasted just three minutes. “J’ai été trompé lâchement,” Lassudry protested: I have been rottenly tricked.

In his final letter, Lassudry told his mother: “God knows when you will get this letter. Maybe in a year, or even two.” There was a postscript: “I shall die on Tuesday December 10th at 9 o’clock. Your loving Henri.”

A senior MI5 officer, Colonel William Hinchley Cooke, went to see the attorney general, Sir Donald Somervell, to inquire whether the belated discovery of the true name, nationality and motivation of one of the men who was due to die in a few days’ time might, in any way, call for a stay of his execution. “I gather,” Hinchley Cooke recorded rather laconically in the agency’s files, “that he thinks it does not.”

Meier went to the gallows first, followed minutes later by Lassudry, who was executed under the name Jose Waldberg. At 9.25am, a two-paragraph communiqué written by MI5 informed Fleet Street and the BBC that the two men had been “apprehended shortly after their surreptitious arrival in this country”, with a wireless set and a large sum of money; that they had been tried and convicted, and hanged that morning. The communiqué added: “Editors are asked not to press for any additional facts or to institute inquiries.”

Seven days later a second notice announced the execution of Kieboom. No mention was made of Pons.

Lassudry’s family never received his letters. The Home Office handed them instead to MI5, along with a covering letter that said the condemned man’s criticisms of the English justice system “would prejudice the letters from our point of view, if there is any question of forwarding them to their destinations”.

MI5 filed the letters away and, in 2005, they were quietly deposited at Kew, where they lay for years, apparently unnoticed. By that time, several histories of Operation Lena, and the capture, interrogation and execution of “Jose Waldberg” and the other invasion spies had already been written.

Does Lassudry’s fate amount to a miscarriage of justice? There is no doubt that he was working for the Abwehr: he had sent three brief radio messages from the beach at Dungeness before his capture. On the other hand, it appears likely that the members of the Old Bailey jury who had acquitted Pons – to their enormous credit, given that the nation believed an invasion to be imminent – would also have shown mercy to Lassudry, had they heard his story.

Between 1940 and 1946, 19 spies and saboteurs were prosecuted under the Treachery Act and executed. A 20th spy – a junior Portuguese diplomat – was sentenced to death, but his sentence was commuted to life imprisonment following the intervention of the Portuguese government.

Facebook Twitter Pinterest Letter relating to the case of Carl Meier and Jose Waldeberg. Photograph: National Archives in Kew

As each case came to court, senior MI5 officers became increasingly concerned that the in camera procedure being used at the Old Bailey was too insecure. They were also troubled by the requirements that notices of execution be posted on prison gates for 24 hours before a hanging, and that a coroner, sitting with a jury, must conduct an inquest into the death of the hanged man. The remedy, one MI5 officer suggested, would be to court martial spies at military establishments and then shoot them. There would be no prying journalists, no need for execution notices, and no coroner’s juries.

The Home Office was uncomfortable about the prospect of mounting courts martial for foreign nationals who were not members of any armed forces, and resisted the idea. However, one spy was dealt with in this manner after he was found to be a former soldier and a reservist in the German armed forces.

Josef Jakobs, a 42-year-old dentist, had been captured in February 1941 after breaking his leg when he parachuted into Huntingdonshire. After a two-day hearing at Chelsea barracks in London, he was driven to an indoor shooting range at the Tower of London, where he was strapped to a chair and shot by an eight-man firing squad from the Scots Guards.

The official communiqué that announced the manner in which Jakobs met his death caused a sensation in Fleet Street. Reporters from the Daily Express tracked down people in Huntingdonshire who had witnessed the spy’s capture, and the newspaper told the official censor that it intended to publish and be damned. Swinton, Maxwell and Somervell met, and agreed that the press should perhaps be given a little more information about the secret prosecutions and executions, to ensure there was no further breach.

The Treachery Act was suspended in 1946, and repealed a few years later. During the war, MI5 could never be sure exactly how many of the Abwehr’s agents had been captured and either prosecuted and executed, or turned and run under British control. After the war, the agency established that just one Abwehr agent had operated without detection, and he had shot himself in an air raid shelter in Cambridge after running out of money and food.

The “great structure of intelligence and counter-espionage” that Swinton had described in his letter to Maxwell, and the wider allied campaign of strategic deception of which it had been a part, had been a remarkable success; possibly one of the finest in the agency’s history.

• Ian Cobain’s study of official secrecy in the UK, The History Thieves, is published by Portobello Books on 1 September.