Journalists should probably always contact the police when seeking a criminal case update. Well, in most cases, perhaps. Let me explain. Over the years, my insider information about underworld bosses and absconding fugitives has earned me respect, possibly grudgingly, from officers of the law. For instance, a police press officer once told a rival news hack: “Ask Martin Brunt, he knows everything before we do.”

That hasn’t always been true, but as Sky News’ long-standing crime correspondent, I’ve often scooped Fleet Street.

From the infamous Cromwell Street murders to the disappearance of Madeleine McCann, I’ve been at the heart of some of the biggest news stories of the last 30 years.

And yet, unbelievably, one of my biggest exclusives came after a criminal had been caught and charged.

Notorious diamond thief Danny Jones was languishing in Belmarsh prison awaiting trial when he sent me a bizarre letter from his high-security cell.

He wrote: “Hello Martin, I have some interesting news for you. I’ve told the Flying Squad I want to give back my share of the Hatton Garden burglary. I want them to take me out under armed guard with my solicitor and yourself.”

The daring raid by his ageing gang of seasoned villains – soon dubbed the Diamond Wheezers – had captured the imagination of the public and made headlines around the globe. Now Danny was promising to lead detectives to the north London cemetery where he had buried a bag of gems, gold and cash, his share of the loot from the £15million heist in April 2015 at the Hatton Garden safe deposit vault.

And he wanted me there as a witness. Not a bad start to a crime reporter’s day. It’s a pity it didn’t quite turn out like that.

To begin with, I thought Danny might be bluffing and winding me up into broadcasting an untrue story that would make me look stupid. And it seemed the detectives didn’t believe him, either. They had turned down his offer.

Scotland Yard tried to dissuade me from reporting anything, warning me that, even if Danny was telling the truth, the hidden jewels he wanted to show them might be another gang member’s share, and the publicity could threaten his safety inside jail. Did I really want to risk grassing up a grass, I was advised.

And could I trust a criminal?

I did what I often do at such career-defining moments: I followed my instincts, trusted my source and took a deep breath. Then I broadcast the story. Bingo!

A posse of armed police in a fleet of Range Rovers turned up at Belmarsh and, with a helicopter shadowing their journey, drove Danny to Edmonton cemetery, which had been sealed off.

Oddly, I wasn’t asked to join them, but Danny’s solicitor Mark Davies was and told me afterwards: “It was like a mafia funeral. There were eight high-value unmarked cars all lined up inside the entrance, and at least six machine guns dotted round the place.”

Danny pointed to the grave of a relative and police very quickly lifted the stone to reveal a holdall containing £500,000 worth of jewels. The discovery also revealed how Danny and the Flying Squad had been playing a game of double bluff.

What detectives hadn’t told Danny was that they had already found what they thought was his only stash, in another grave.

But he had buried two holdalls in different graves. The police assumed he was offering to show them the one they had already recovered. So that’s why they’d been so reluctant to take him out of prison!

Danny, in his ignorance, had hoped he could show them one stash and return, after completing his sentence, to dig up the second one as his pension. Danny and his gang were caught because of simple mistakes they made, not realising that, in the years since they began their villainy, technology had developed all sorts of detection and surveillance methods.

The commander of the Flying Squad called them “analogue criminals in a digital world”.

But their antics thrilled TV news audiences and newspaper readers – and prompted three films starring Hollywood actors, illustrating the public’s enduring fascination with true crime.

It’s often the more grisly aspects that have true crime fans riveted, one of the themes I explore in my new book No One Got Cracked Over the Head For No Reason and a phenomenon that’s kept me in my job for so long.

Another of the old-school villains I got to know is Freddie Foreman, now in his nineties, a much-feared and respected gangster from South London who was jailed for handling the proceeds of the £6million Security Express cash robbery in 1983.

I once asked Freddie, a man with a fierce temper and a dry sense of humour, what he told his wife when he went out to commit a crime. “Well, I didn’t say, ‘Darling I’m just off to stick up Barclays. I told her I was going out to do a bit of work and see you later.’”

How much later Mrs Foreman saw Fred depended on his success.

We met as he strolled in glorious sunshine across the clipped lawns of the Ocean Club in Marbella, on the now notorious Costa del Sol in southern Spain.

The coast had become known as the “Costa del Crime” because Fred, and other notorious, wanted villains were untouchable to British police impeded by the then absence of an extradition treaty.

Freddie and I, both booted and suited, were there for the lavish wedding of another villain, Ronnie Knight.

The difference was that Freddie was invited and I wasn’t – but nor were all the other hacks, photographers and undercover Flying Squad detectives hiding in the Bougainvillea bushes.

During the reception, a slightly-sozzled Knight wobbled towards us with a tray of brimming champagne flutes, plonked it unsteadily on the grass and growled: “Here you are guys. Thanks for coming. Now drink up and f*** off.”

One by one, the old runaways eventually chose to return or were forced back to face British justice. But the area remains a magnet for fugitives who can disappear into the large expat community, support themselves with a bit of drug dealing and enjoy the two biggest attractions of hot sun and cold beer – at least until a copper or crime reporter catches up with them.

I’ve had tip-offs from expats who recognise a Most Wanted suspect on the news or are simply suspicious about a dodgy neighbour.

Viewers love to play detective.

Benefit fraudster Norman Brennan, 70, was walking his dog in a park near his Spanish apartment when I approached and introduced myself. “And?” he replied, rather annoyed to have his evening stroll interrupted.

He’d been wanted in Liverpool for five years for claiming £120,000 in benefits by pretending to be his brother.

Department for Work and Pensions investigators had been trying to track him down, while their oblivious colleagues in the DWP payments section had been sending him his pension every month. Ex-Secretary of State Sir Iain Duncan Smith was suitably outraged at our exposure of his staff’s laughable incompetence, though if heads rolled they certainly didn’t include his. In Northern Cyprus, the Turkish-controlled part of the divided island that still has no extradition treaty with the UK, fugitive Wayne Smith asked me to help him give himself up to the British consul in the south.

Wanted for causing death by dangerous driving during a race through a Birmingham street, he and his girlfriend, also a fugitive, were fed up with their life on the run.

“This is no holiday lifestyle here,” he told me. “We have no money and struggle from day to day to make ends meet.”

He poured out his heart as we sat sipping coffee on a curve in the sand of a beautiful pine-fringed beach.

Trapped in paradise. I shouldn’t have, but I couldn’t help feeling just a bit sorry for him.

Despite my record, I haven’t pursued the most famous fugitive of all: Lord Lucan, the earl accused of murdering his children’s nanny at the family’s Belgravia home. Plenty of journalists have chased sightings of him across the world.

One of them is my late colleague Garth Gibbs, who had so much fun chasing Lucan that he counted it as his career highlight and reckoned he was glad he never found him.

He wrote: “I regard not finding Lord Lucan as my most spectacular success in journalism. I have successfully not found him in more exotic spots than anybody else.

“I spent three glorious weeks not finding him in Cape Town, magical days and nights not finding him in the Black Mountains of Wales, and wonderful and successful short breaks not finding him in Macau either, or in Hong Kong or even in Green Turtle Cay in the Bahamas, where you can find anyone.”

Conman Mark Acklom, who had duped a British woman of all her money in a romance scam, asked me from his prison cell in Geneva if Sky would lend him €30,000 bail money.

He promised to pay it back as soon as he was freed. Before you ask, we didn’t.

Villains aren’t the only ones who’ve made bizarre requests of me.

A senior detective involved in a complicated corruption case once complained to me, over a coffee near my Westminster office, that his suspects were too clever to be caught out by listening devices hidden in their phones and cars.

He asked if my employers would consider putting a bug inside a target’s satellite TV system. It would need our technical department to create a “fault”, he explained and then send round an engineer to “correct” it.

I passed on the request, but I knew the answer would be a firm no and not a polite one. It was probably a wise decision.

No crime reporter wants to be exposed as a police snitch.

Martin Brunt is Sky News crime correspondent and author of No One Got Cracked Over the Head for No Reason (Biteback, £20). To order visit expressbookshop.com or call Express Bookshop on 020 3176 3832. Free UK P&P on orders over £25