They appeared to be the perfect neighbours - unassuming, hard-working and polite. But Fred and Gwen Edmunds had a dark secret.

To their business colleagues they were two poultry farmers doing their patriotic bit for the war effort.

But a spy dossier has revealed they were at the centre of a failed international fascist conspiracy to smuggle escaped Nazi prisoners of war across the world.

The dossier - part of 198 top secret MI5 files made public for the first time on Friday - contains letters intercepted by the Home Office and transcripts of bugged phone calls to the couple and other conspirators, as well as reports by spooks watching the group.

It was 1946 and the war had been won when the couple first came to the attention of the security service.

MI5 agents were following the movements of the leader of the British ultra-right-wing Imperial Fascist League, the fanatical anti-Semite Arnold Leese.

They became suspicious that the Edmundses, former members of his organisation, may have become involved in a plan hatched by Leese to assist escaping Nazis to South America.

The couple, who had boys aged 12 and 13 and daughters aged two and 11, were respected in Worthing as important local employers who led a quiet, private life together.

But an MI5 file concluded: "The man and wife seemed to be inclined to National Socialism and quite pro-German."

Internal security service memos reveal that Dutch Nazis Herman Meijer and Hendrick Tieken, SS stormtroopers who had escaped from Kempton Park prisoner of war camp in 1946, made contact with Leese, who conducted them through a series of hiding places until they settled in Littlehampton Road, where police eventually arrested them in 1946.

Although it has since been public knowledge that Fred Edmunds was convicted for hiding the men and sentenced to 12 months in prison, the dossier contains much information never before seen and demonstrating the extent to which he and his wife had become involved in Leese's conspiracy.

It also reveals it was Fred Edmunds who took the blame for his wife, who went unpunished despite being named by spies as the one who "wears the trousers in this household".

A surveillance report by spies watching the Edmundses circulated before they had even met the prisoners reveals: "Arnold Leese, AW (Tony) Gittens and other fascists are helping two prisoners of war who escaped in June or July and have since been given refuge in the house of former supporters of Leese's Imperial Fascist League.

"Leese hopes to assist them eventually to get out of this country.

"Reports from very reliable secret sources say moreover that Leese plans to organise a regular escape route for Nazis from Germany to Spain or South America and to make contact with Nazi nuclei which he believes to be operating there.

"Checks on Leese and Gittens have revealed that Leese is hoping to find temporary refuge for the two Germans with whom he is concerned at the moment with Mrs Gwen Edmunds ..."

The secret service file on the Edmundses contains correspondence between Mrs Edmunds and Leese, whom she called Uncle A, using a code in which the prisoners of war were referred to as "cousins" or "dogs".

In one letter she writes: "The cousins are very well and full of life. We grow very fond of them."

Spies concluded from the intercepted letters that the Edmundses were almost certainly feeding and clothing the escapees and giving them money.

But they left their bolthole only once, on a day trip to Brighton, and police were unable to ascertain for sure where the men were being hidden.

Top MI5 officials were reluctant to involve local police because they feared the Edmundses might get wind that plans for the larger operation were about to be uncovered.

In one internal memo an MI5 official says: "The arrest of the fugitives might conceivably give Leese and his accomplices such a severe fright that they would abandon their long-term project of organising an escape route for Nazis from Germany and linking up with Nazi nuclei abroad.

"It might, on the other hand, result in their suspending activities temporarily and resuming later along lines even more difficult for us to follow."

Security chiefs held a meeting with Supt Catt and Insp Eagle, of Worthing Police, on November 6, 1946.

Things came to a head when spies shadowing Leese and the Edmundses realised the prisoners were to be given identity cards and shipped to Eire.

Police raided the Edmunds' home early on the morning of Sunday December 15. They pretended they had been looking for someone else but arrested the prisoners they found sleeping in the loft.

Leese, Fred Edmunds and five others were convicted at the Old Bailey in March 1947 of hiding the prisoners.