The Auschwitz commander who oversaw the deaths of 2.5 million people was captured and interrogated by a Jewish soldier.

Liverpool-born Karl Louis Abrahams was part of the team which tracked down Rudolf Hoess, the man in charge of the death camp in Nazi-occupied Poland from 1940 to 1943.

The arrest was made on March 11 1946, 70 years ago this week.

Hoess introduced the use of Zyklon B in the camp's gas chambers, which could killed 2,000 victims in less than an hour, and confessed in 1946 to being responsible for 2.5 million deaths - most of them Jews.

Sergeant Karl Abrahams joined the British Army Intelligence Corps in 1942, but it was not until 1946 that he was given the mission of his life, to apprehend who he called "the most diabolical criminal in all human history".

In letters written to his wife Betty throughout the war and handed over to the Israeli Holocaust memorial centre Yad Vashem upon his death, Mr Abrahams revealed his part in hunting down Hoess.

Writing on March 13 1946, he told Betty: "The past few days have been crammed full of excitement and high-pressure work. After months of patient toil, we've made a big scoop about which you may read something in the newspapers fairly soon.

"I can't tell you any more than that except to say that we are working most times well into the night and often until the wee small hours."

It was only 11 days later that he revealed the whole truth, telling his wife of 13 years: "After our capture of Rudolf Hoess - did I tell you by the way - everything seems like an anti-climax."

Describing Hoess as "the greatest swine that ever was", he said that after five months of working on the case, it was "a great satisfaction to have got him at last".

He added: "His interrogation was an experience I shall never forget. We were at it for about three days and two nights on the trot. No sleep - the atmosphere was weird and unreal as we heard him confessing that he had personally supervised the gassing and burning of over two and a half million human beings - mostly our fellow Jews."

The capture was made possible after his team tracked down Hoess's wife Hedwig, who during her interrogation told them that her husband was sheltering in a farmhouse near the Danish border in Gottrupel, under the name of Franz Lang.

After members of the team including Mr Abrahams extracted a confession from Hoess, the former Nazi commander went on trial in Poland in 1947 and was hanged in April at Auschwitz, next to the crematorium.

Mr Abraham's son Stephen, who kept his father's wishes that his wartime letters be handed over to Yad Vashem after his death told the JC that his father was a "very quiet and modest" man who never spoke to his family about the mission.

"There are many people in our community proud of blowing their own trumpet. This was not the case with my father," he said.

This business-like attitude was shown in the final sentence of Karl Abraham's letter about the arrest, which read: "However, that's that and now we must keep going on all sorts of other jobs."

Stephen Abrahams, 71, said his father, who in his later years was a JC correspondent in Liverpool, "didn't talk about it, and we never pressed him to.

"He must have kept these documents secure and filed away, and it never came up. It's similar to survivors who for many years do not want to talk about their experiences. My mother didn't talk about it either, so we just didn't."

Stephen, from Solihull, said he thought his father, who died in 1980, "was just concerned about bringing up his family the best he could, without going back and telling us about his experiences".

But after finding out what his father had achieved, he said: "It's an emotional thing. I feel proud of him. My father was a gentle, retiring, educated man, proud of his Jewish heritage and a devoted family man.

"What his thoughts were about coming face-to-face with and interrogating such an evil man, it is so difficult to comprehend."

Accepted to the Intelligence Corps because of the fluent German he had learned at school, Karl Abrahams worked in port security in Scotland and Liverpool before being posted to Germany after the war was won.

In October 1945 he was given, along with several others, the task of finding Hoess, but the first part of the investigation was difficult. As he wrote in November 1945: "At long last, it is Sunday and with it comes a brief respite from this dizzy round of Nazi chasing.

"I never shall like it or get used to it over here. Having to deal every day with unpleasant Germans -what I find more nauseating [is] fawningly polite Nazis trying to ingratiate themselves."

His experiences of the war and of Germany had changed his perspective, he said. "I am gradually becoming disillusioned about the whole business of reforming Germany and leading her people back to the light.

"I no longer work with a spirit of idealism and yet I can't reconcile myself to being selfishly materialistic and just look after myself."

Karl Abrahams wrote regularly to Betty after being posted abroad. Along with the arrest of Hoess, he described the horrors of post-war Germany, writing in June 1945: "I have found the site of a school here. It is now just a piece of wasteground.

"It was apparently completely obliterated by the chazerim (Yiddish for 'pig flesh',) - that's much too mild a term [for the Nazis], I know."

A month later he travelled to northern Germany, writing home to tell of the destruction he saw. "Arrived here at Kiel - came through Hamburg and Hanover and saw indescribable scenes of ruin. Vast areas, literally miles of a large city, in complete ruin - a heap of rubble with practically nothing standing."

He missed home, telling Betty in December 1945: "It's a great pity I couldn't be home for Chanucah, which should be starting any time now I should think. I will just have to picture the scene of ceremony at home with the coloured candles lit."

In May 1946, when he received the news that he was being allowed to go home, he wrote: "I'm so excited about it that I can hardly settle to anything at all now. I can honestly say that I've put in more hours of continuous toil in the last six months than ever before."