High above the sleepy German town, the twilight gave way to darkness as a detachment of soldiers strode purposefully through the castle corridor. They stopped at a door and, exchanging knowing glances with the men keeping guard, entered the room. Acting in military unison, they placed their hands on the prisoner, pulled him to his feet and marched him up the stone spiral staircase that wound its way to the attic rooms at the top of the most famous prisoner-of-war camp of the Second World War.
The prisoner, a sub-lieutenant in the Royal Navy, was visibly shaking as he tried to come to terms with the desperate circumstances in which he now found himself.
This was no Nazi court: the men gathered in that half-lit room at the top of Colditz Castle on March 11, 1944, were all British officers, bent on a rough kind of justice.
They had good reason to believe that the man before them, Lieutenant Walter Purdy, was a spy sent into Colditz by the Germans to betray his countrymen.
Purdy intended to reveal British escape plans to his German handlers, including a secret tunnel that had taken six months of back-breaking work to complete, and which scores of men were now counting on as their best bet for rejoining the war. The tunnel was the 15th to be built, and the most technologically advanced yet; constructed to defy detection by the German ‘tappers’ whose job it was to locate suspicious voids in the castle’s structure.
Purdy told the British interrogators who now surrounded him that he had made a terrible mistake; he had stupidly backed the wrong side, and pleaded for leniency.
The men gathered in that half-lit room at the top of Colditz Castle on March 11, 1944, were all British officers, bent on a rough kind of justice
But surveying the vengeful faces of the British officers, he must have realised there could be no reprieve, and the best he could wish for was a quick death.
Finding a suitable rope for the grisly task was no trouble – in a prison obsessed with escaping, rope-making was a common pastime. All that was left was to find a man willing to be hangman.
But despite the horrors of war all had witnessed, none of the soldiers that day was prepared to kill, in cold blood, one of their compatriots – no matter his crimes.
Reluctantly, they handed Purdy back to the Germans. And that act of mercy left him free to cause considerably more harm.
There was more at stake at Colditz than just thwarting escape plans. The Nazis had long suspected that the British PoWs detained at the notorious prison had also established a secret communications system to transmit vital intelligence to London.
The Colditz commandant and his head of security, Captain Reinhold Eggers, working closely with German military intelligence, the Abwehr, and the feared secret police, the Gestapo, had invested substantial resources in cracking this system, including planting French and Polish spies and using clandestine listening devices.
But the Germans had been unable to stop the flow of secret messages leaking out of the castle.
A key reason for this was a new branch of British military intelligence, MI9, which had been given the task of aiding Allied escapers and evaders in occupied Europe.
It set up a cell of British coders operating from within the prison under the nose of the commandant, using encrypted codes hidden in letters written to their families.
MI9 intelligence officers devised ingenious methods to smuggle in escape equipment in parcels, clothes and letters including maps, compasses, blades and metal files, as well as intelligence to help the PoWs with their clandestine work. These were all put to good and enthusiastic use.
This valuable communication line fed intelligence to the War Office, identifying RAF bombing targets, German air defences, U-boat bases, troop movements, and the whereabouts and identities of a group of VIP prisoners whom the Nazis had secretly brought to Colditz as hostages.
But the stakes were high. If the Germans broke the codes, the Allied prisoners risked being shot as spies. Two escape tunnels dug over seven months had been uncovered, so the British PoWs were convinced there was a ‘stool pigeon’ in their midst.
The Germans’ hunt for suitable collaborators among the PoWs, and the British efforts to smoke out the collaborators, consumed a great deal of time and energy on both sides. Each PoW had his own personal theory about who might be a camp spy: the officer caught having a quiet word with a German guard in one of the dark castle corridors; the prisoner who had come into possession of a box of fresh eggs; the bolshie orderly who wouldn’t take orders; or maybe the officer who had no interest in escaping. A prisoner didn’t have to do very much to raise the suspicions of his fellow captives, especially if his face didn’t fit.
But by 1944, Captain Eggers still didn’t have the key intelligence he was looking for. He needed a personal spy, someone who could insinuate himself into the heart of the British security structure in the castle. The Gestapo knew just the man, one who had already shown willing to betray his country: Walter Purdy.
Purdy was a working-class fascist sympathiser from London’s East End who, as a teenager, had attended Oswald Mosley’s rallying speeches. He had also met leading lights of the British Union of Fascists, including William Joyce, nicknamed Lord Haw-Haw.
He hadn’t asked to join the Royal Navy, or expected to find himself bearing arms against the Germans. But as a junior mechanic on the Blue Star Line cruise ships, he was hastily pressed into the service of the King when war broke out in 1939, and transferred to the Royal Navy troop transport ship HMS Vandyck as a sub-lieutenant.
The ship was sunk off Norway in 1940 and the surviving crew, including Purdy, were captured and taken to the newly built Marlag PoW camp near Sandbostel, in northern Germany. Prison life was not to Purdy’s taste. He stood out, freely speaking about his desire for a fascist regime to replace the British Government, and told everyone who cared to listen that Britain was weak and heading for a calamitous defeat.
The camp’s Scottish dentist, Julius Green, who was carrying out secret work serving British Military Intelligence, had noticed Purdy and considered him a jumped-up rabble-rouser.
Green, who was Jewish, had devised a form of invisible ink from chemicals the Germans had given him to carry out his dental procedures, which helped him send messages back to London.
He was also one of only a handful of trusted covert British operatives who knew the most up-to-date MI9 communication codes – so he had more pressing matters to attend to than Purdy.
When he was transferred to another camp, Blechhammer in Nazi-occupied Poland, he needed an ally to carry on his secret intelligence work – and he found it in John ‘Busty’ Brown.
The 6ft gunner, a battery quartermaster, had received training from MI9 in how to carry out clandestine activities after capture. Brown had cosied up to the German guards by bartering Red Cross luxuries. In return, he was allowed on unescorted visits to nearby foreign labour camps, and was permitted to write an article about life in a German PoW camp that was warmly received by Joseph Goebbels’s office of propaganda.
Purdy intended to reveal British escape plans to his German handlers, including a secret tunnel that had taken six months of back-breaking work to complete
This ruse was so successful his own room-mates were suspicious of him, and believed he was anti-British. In fact, Brown was escape-planning; making lists of helpful contacts and safe houses across Europe that would form the basis of a secret escape line for Allied PoWs. What he did not have were the communication codes.
So when he was summoned to Berlin as personal thanks for his article, it was a real chance to gather crucial intelligence and strike back at the heart of the Nazi citadel.
Green reasoned that Brown could be a unique asset, so spent many hours teaching him the codes.
But the Nazis, as it turned out, had plans of their own for Brown. In Berlin, he was taken to meet Alexander Heimpel, a officer with the Abwehr, whose job was to turn Allied collaborators into spies to work inside the prison camps, infiltrate the escape networks and break the British communication codes. Brown was interviewed for the ‘job’ by William Joyce, Lord Haw-Haw himself, who had fled Britain shortly before the declaration of war. It was too good an opportunity for Brown to refuse. And it was, in the end, how Brown and Green unmasked Purdy as a German spy.
In May 1943, Joyce had also marked Purdy as a possible Nazi collaborator and invited him to leave Marlag to join him in Berlin at a special camp, Kommando 999. This was a new kind of Nazi propaganda experiment, a PoW ‘holiday camp’ for British officers who the Germans said deserved a break after three years of captivity.
British ‘guests’ were given regular hot meals, cigarettes and as much beer as they could drink on Fridays. Orchestras entertained the men, while coaches were laid on for sightseeing tours of Berlin. The Germans even arranged river cruises at weekends. The true intention, of course, was more sinister: to ‘turn’ them into assets.
And Purdy stood out. He lectured his fellow PoWs about the advantages of Nazi rule, and how the Jews had brought the British Empire to its knees.
After a few weeks, Purdy was asked to visit Heimpel, who offered him the chance to become a broadcaster, sending propaganda over the airwaves to British fascist sympathisers. The broadcasts received relatively wide audiences in Britain because they offered a rare window into what the enemy was thinking.
Purdy knew this was crossing a line. But with Europe then under the complete control of the Third Reich, he reckoned he could afford to chance his arm.
The most likely scenario was that the British would do a deal with the Germans and there would be some kind of settlement in Europe. If that turned out to be the case, he would be safe from British retribution and would have spared himself several years of life-sapping imprisonment.
He was assigned a new identity – as Robert Wallace, a Buenos Aires businessman – and a freedom pass granting him unhindered travel. But with relentless Allied air raids over Berlin, the Nazi high command realised there may be little left of urban Germany worth fighting for.
PoW spies, including Purdy, were ordered to gather any intelligence that might give them the edge.
Brown, meanwhile, was given leadership of another holiday camp, Special Camp 517, where he was – under the nose of his German commanders – turning the PoWs to his own advantage, picking up vital intelligence about the movement and whereabouts of German military units, which he passed on to London.
One of the star turns at the camp was British-born opera singer Margery Booth, who had been recruited by MI9 in Berlin and was risking her life sending messages back to London. Known as ‘the knicker spy’, she regularly concealed documents in her underwear. Soon, she was also helping Brown. MI5 was keen for more information on British traitors and Brown was asked to get to work.
What he found had serious ramifications for the next stage of the war. A dying young soldier, Carl Britten, admitted to Brown that the reason Germany needed so many collaborators was to establish an elite force of British fighting soldiers to form a unit, the British Free Corps, in the Waffen-SS. This could cause serious damage to morale on the front line.
The tunnel was the 15th to be built, and the most technologically advanced yet; constructed to defy detection by the German ‘tappers’
Then, while searching a property in Berlin, Brown stumbled across a suitcase in a cupboard. There he found a letter, signed by ‘Lt Commander W Purdy’, in which he set out his reasons for wanting to work for the Germans, signing off with ‘Heil Hitler’.
Brown had heard this name before. Soon after Julius Green had arrived at Blechhammer, he’d told Brown about his time at Marlag, and a naval engineer called Purdy who was extremely pro-German. Now, Brown knew that Purdy, who had obviously promoted himself, was no longer just a PoW.
He knew he had to inform London, so he persuaded Heimpel to let him go back to Blechhammer, ostensibly to recruit more German-friendly PoWs, but where he told Green about Purdy’s betrayal.
Green sent a coded letter advising his MI9 handlers that the British naval officer had been turned and was now a dangerous Nazi spy. The message was the last Julius was able to send. A few weeks later, in January 1944, the Nazis transferred him to a more secure camp: Colditz.
That year, Heimpel found himself head of counter-intelligence for all PoW camps, and one mark of achievement to justify the faith his Nazi bosses had placed in him would be to secure an intelligence breakthrough from inside Germany’s most important camp. He told the prison’s security officer, Eggers, that he intended to place informants inside the castle. Shortly afterwards, in walked Purdy to join the prisoners – unaware he was about to be unmasked.
It didn’t take long for one or two officers to recognise him from Marlag. But one appeared to be very pleased to see him. Captain Julius Green welcomed him as if they were long-lost comrades, showing him around the castle. But as he did so, the two men encountered Lieutenant Ian Maclean emerging from a wooden flap opening above a stone lintel.
This was the entrance to a secret tunnel known as Crown Deep, which had almost reached the outer walls of the castle’s northern boundary. Maclean had finished his shift and was being relieved by another digger.
It was the tunnel upon which the British had been pinning their escape hopes, the one that would deliver them their freedom before the end of the war.
Green later learned Purdy had already discovered the whereabouts of the hide, which contained a cache of escape equipment, the camp radio and a stash of German currency. Just 36 hours into his mission, he had uncovered enough intelligence to satisfy both Heimpel and Eggers.
Green was furious. Confronting Purdy, he made it clear that his treachery had already been uncovered by Brown in Berlin, and relayed back to London. Under interrogation by officers, he admitted to being ‘a traitor and a rat’ and was placed under guard. But at the hastily arranged court martial that night, which found him guilty of treason, none of the officers had the stomach for a lynching.
This left the British with a very serious problem. If they let Purdy live, he would betray them all – including Brown and his spy operation in Berlin, which Green had unveiled on the basis that he believed Purdy to be as good as dead. That indiscretion jeopardised Brown’s life. But, in a stunning irony, it helped save Purdy from the hangman’s noose a second time. The men turned Purdy over to the Germans and, sure enough, a few days later a search party entered Colditz and smashed their way into the base of the circular staircase to reveal the entrance to the tunnel the Germans had searched for for so long.
Eggers said he had been acting on a long-held hunch. But the British knew exactly who had betrayed them and their tunnel.
After the war, it was evidence obtained by Brown that helped convict Purdy.
While clearing out an address in Berlin that had been used by the Germans to house Allied PoWs they were keen to cultivate as traitors, Brown had found letters torn up in a wastepaper basket that were part of a chain of correspondence between Purdy and senior Nazis, including one written to Eggers informing him about a system for getting letters out of Colditz.
Brown had microcopies made and stored in a secret cavity in the heel of his shoe. And the original letters were given to the one agent Brown thought had the best chance of keeping them safe until the war was won – Margery Booth, the knicker spy.
On the morning of December 18, 1945, Walter Purdy was brought from prison to the cells at the Old Bailey. He was convicted of two counts of high treason, but acquitted of the most serious charge: informing on the prisoners of Colditz. Sentenced to hang, he was saved from the gallows by a last-minute pardon by the Crown. Had the prosecution done a deal with Purdy?
The jury had not been given details of the PoW court martial at Colditz, or of the aborted lynching by his own side. To this day, the MI5 files remain selectively sieved so the event is not officially recorded. It was a grim moment in the history of Colditz, and reflected badly on the British, who had always claimed to hold themselves to higher standards than the Nazis.
But the officers’ failure to carry out the hanging had placed the lives of Brown and Green in danger and risked the security of the Berlin spy ring. The whole affair was an embarrassment and showed the heroes of Colditz in a different light. And Purdy, according to one MI5 report, became the ‘greatest rogue unhung’.
© Robert Verkaik, 2022
The Traitor Of Colditz, by Robert Verkaik, is published by Welbeck on July 7 at £20. To pre-order a copy for £18, go to mailshop.co.uk/books or call 020 3176 2937 before July 10. Free UK delivery on orders over £20.