The 50th anniversary of the Great Train Robbery was yesterday, a red letter day for a Rainham man who has been inundated with requests to speak about his unusual friendship with one of the robbers - Ronnie Biggs.

For the nine-year-old boy standing outside Wandsworth Prison one day in July 1965, the red removals lorry he saw alongside its towering walls was to lead to a fascination with Great Train Robber Ronnie Biggs.

Only minutes before, Britain's most notorious escapee had scaled those very walls on a rope ladder, jumped onto the van's roof and made off in a getaway car to begin 36 years on the run.

Fifty years from the heist that netted the gang an unprecedented £2.6million in cash – worth about £55 million today - that boy, Mike Gray, is swamped with media requests to talk about his personal relationship with Biggs, which now stretches back over a quarter of a century,

It was on August 8, 1963 that Biggs teamed up with criminal mastermind Bruce Reynolds and the other ruthless accomplices to hold up the Glasgow to London overnight mail train.

Like all the others, Biggs was caught and sentenced to 30 years in prison. But within 15 months, he had absconded - fleeing to France, Spain, Australia and finally Brazil.

Young Mike Gray had been outside the south London prison because his father was a warder there and his family lived in locally-provided quarters.

After Britain's failed attempt to extradite Biggs from Brazil in 1974, Mike found out his secret address and wrote to him, explaining their chance connection.

The famous fugitive responded and ever since Mike, now 56, has paid him regular visits.

From 1989, Mike wrote to or telephoned Biggs every month and in 2001 visited him in Belmarsh Prison after his return to Britain – the first time the two met face-to-face

Since then, Mike has helped set up a website with Biggs' Brazilian-born son Michael, become UK organiser of the Free Ronnie Biggs campaign after he returned from Rio and written a book, Ronnie Biggs – The Inside Story.

Biggs was finally granted his release in 2009 on compassionate grounds. He suffered a series of strokes from which he was not expected to recover.

Mike said: "I visited him in prison and he was very ill and I thought he might even pass away. It was then I wrote and sang Ronnie Biggs – Knockin' on Heaven's Door. It's had 26,000 hits on YouTube."

A couple of months later, he met his friend as a free man for the first time and handed over his book.

But why the fascination? Speaking from his home in Lower Rainham Road, he said: "It started in the shadows of Wandsworth Prison.

"He regrets going on the run as it destroyed his family..." - author Mike Gray

"Ronnie has never been a hardened criminal, he was the 'tea boy' who became 'the legend' via the world's media/press.

"The world press have created this monster – Ronnie Biggs – notorious hardman, something he laughs about. But he regrets going on the run as it destroyed his family.

"I last saw Ronnie in February. He had a cancer growth removed last year on his forehead and is still wheelchair-bound, cannot speak and is still suffering the effects of his third stroke some years ago, but his mind is as sharp as ever."

Yesterday was not only the 50th anniversary of the robbery, it was also Biggs's 84th birthday.