'Hitler's only friend' who died in the city he tried to bomb into defeat: How Nazi war criminal Albert Speer passed away in London while making BBC programme - after saving himself from hanging by claiming ignorance of the Holocaust

He was the self-styled 'good Nazi', the man who sanitised his reputation despite spending years as the 'only friend' of Adolf Hitler.

Albert Speer, the chief architect of Nazi Germany who became armaments minister, spent 20 years in prison after being found guilty of war crimes at Nuremburg. 

But he went on to remodel himself in a bestselling memoir, claiming he had no knowledge of the plan for the Holocaust.

Yet a new documentary airing on Sky History reveals how those claims were false, by showing that he was in charge of the expansion of Auschwitz, including the construction of gas chambers where Jews were murdered. 

Speer's apparent contrition and regret saw him come to London in 1973 for an interview with the BBC amid fierce controversy which led to him being held at Heathrow Airport for eight hours. 

And he was in London - the city that was hit by bombs made under his direction - when, while making a documentary with the BBC, he collapsed and died in September 1981. 

Speer had first come into contact with Hitler in 1933, when he was site manager on the renovation of the Chancellery in berlin.

The married father-of-six soon established a close bond with the Nazi leader and was put in charge of rebuilding Berlin, to turn it into a 'world capital'.

The grandoise new Chancellery he built for Hitler boasted a 480foot-long hall and a polished stone floor. 

The stone for the projects was quarried by 10,000 concentration camp slaves in horrific conditions. 

Speer later said of this fact: 'The Yids got used to making bricks while in captivity in Egypt.' 

When homes had to be demolished for his mammoth projects, 23,000 Jewish apartments were seized and their occupants sent to death camps. 

The architects was appointed Minister for Armaments by Hitler in 1942, three years into the Second World War.

He initially had dramatic success, dramatically increasing the manufacture of weapons.

But he did this by using prisoners of war and millions of slave labourers.

Yet vital factories, raw materials and supplies were lost as Allied bombing intensified and the Russians continued advancing towards Germany.

Speer was then ordered to focus on weapons such as the V1 flying bombs and V2 rockets. 

Slave labourers were again put to work in appalling conditions which saw them toil for 72 hours a week on a meagre diet of 1,100 calories. 

When he was put on trial at Nuremburg after Germany's defeat, he accepted full responsibility for his actions but claimed to have been ignorant of the murder of Jews.

This display contrasted with the unrelenting and unrepentant fanaticism of the other leading Nazis. It enabled him to escape a death sentence.

Instead, he was sent to Spandau prison, where he was held on his own for two decades. Wealthy friends smuggled him delicacies including champagne and caviar.

Following his release in 1966, he published his memoir, Inside the Third Reich. The book, which was a huge success, earnt him a fortune in royalties. 

The tome portrayed him as 'The Good Nazi' who had no knowledge of the murder of six million Jews. 

But following his death, evidence against him mounted. 

As well as his eviction of Jews from Berlin and his brutal use of slave workers, he was known to have been present when Heinrich Himmler, the head of the SS, said it was necessary to exterminate the Jews and their children to prevent future revenge. 

Speer revealed his presence at the speech in a letter he wrote to the wife of a Belgian resistance leader who was killed by the Nazis.

He said in the 1971 letter, which emerged in 2007: 'There is no doubt: I was present when Himmler announced on October 6, 1943 that all Jews would be killed.' 

Speer had previously claimed that he had left the conference before Himmler gave his speech. 

Shown in the Sky History programme Hitler's Engineers are the plans that he oversaw for the expansion of Auschwitz in occupied Poland, so it could accommodate thousands more Jewish prisoners. 

They also detailed the construction of gas chambers and crematoria. 

Speer was interviewed by the BBC's Midweek programme in 1973. 

After the Home Secretary allowed him to come in to Britain for 48 hours, he was pictured in BBC promotional photos reading a newspaper outside Windsor Castle and was also seen in Shepherd's Bush, West London.

Speaking of the moment he was held at Heathrow, he said: 'I was not embarrassed by the fuss. I thought it was quite hilarious.

'It was a little bit boring, but I am used to that. After all, I was in prison for 20 years.'

He added: 'I survived to remain a normal human being. But I could have been destroyed by my sentence, like many of my contemporaries.'

He said he had 'made it clear' what his regrets were from the Nazi period. 

The former senior Nazi also claimed: 'I didn't want to try and destroy London. I saw no point in that sort of warfare by either side. 

'Now I have seen the city I am glad that so many old buildings survived the destruction'.  

He was also interviewed on Thames TV programme This Week in 1975. He called Hitler 'eccentric' and spoke of the moment he was released from Spandau prison.   

On the day he died in 1981, he had spent time on the set of a new BBC documentary about Hitler's plans to plunder the art treasures of Europe.

After returning to his hotel in Bayswater, he collapsed and then passed away a few hours later in St Mary's Hospital.  

Hitler's Engineers airs on Sky History at 9pm tonight.