On 12 June 1962, three men escaped from Alcatraz, never to be seen again. The ultimate fate of Frank Morris and the Anglin brothers remains a mystery but the ingenuity and determination of their daring escape – from what was the US's most secure prison – continues to captivate. Two years later, the BBC returned to the scene of the crime.

In May 1964, BBC Panorama's Michael Charlton made "the most feared journey in the criminal world" across the churning waters of San Francisco Bay to see the infamous prison island of Alcatraz. Nicknamed "the Rock", the federal penitentiary had held some of the most dangerous criminals in the US. It was regarded as an impregnable fortress. But in the early hours of 12 June 1962, three men achieved what was thought impossible: they escaped.

Alcatraz had originally been a naval defence fort to protect the entrance to the bay. During the US Civil War, because of the island's isolation, steep cliffs and the swift, cold currents that surrounded it, captured Confederate prisoners were held there. Early in the 20th Century it was rebuilt as a military prison. In the 1930s, as the US tried to deal with rampant organised crime that flourished during Prohibition, the Department of Justice took it over. Soon the most fearsome convicts from the federal prison system began arriving. Among its more famous inmates were the notorious gangsters Al Capone, Mickey Cohen and George "Machine Gun" Kelly, as well as convicted murderer Robert Stroud, who would later become better known as the "Birdman of Alcatraz". "Men too vicious and troublesome to be held in an ordinary jail," was the way the BBC's Charlton put it.

Four years before Panorama travelled there, Frank Lee Morris had arrived on the island. Orphaned at the age of 11, and convicted of his first crime by the age of 13, Morris had spent most of his life in and out of various correctional facilities. Considered highly intelligent, he was a seasoned criminal, with a charge sheet ranging from drug possession to armed robbery and, perhaps most notably, prison breaks. He had been sent to the Rock in January 1960 following his escape from Louisiana State Penitentiary. As soon as he arrived on Alcatraz, he began to think about how he would leave. He was joined in his cell block by convicted bank-robbing brothers John and Clarence Anglin and Allen West, who had been an inmate on Alcatraz since 1957. All the men knew each other from previous stints in prisons together, and since they had adjoining jail cells, they were able to speak to each other at night.

When the BBC's Charlton visited the site, a year after its closure, he was well aware of the prison's formidable reputation for unrelenting guards, harsh conditions and the punishing sea winds that the convicts had to endure. "A relentless wind which never seems to stop, howls and echoes through the bars," he said. "Built over the rambling passages of an old fort… the foundations today of Alcatraz are rotting and breaking up."

With Morris taking the lead, the four prisoners began to concoct an elaborate and audacious plan to escape. Over a period of several months, the men chiselled away at the salt-damaged concrete around the air vent under their sinks. Using metal spoons........

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