The phone goes. Someone is ringing to offer the news desk of the Sun a very big story indeed.

Let's imagine this time the call came in the summer of 2007 shortly after the Crown Prosecution Service had decided the evidence collected by Surrey Police (true) was not strong enough to charge Jimmy Savile with the sexual abuse of four young girls.

The voice on the end of the line says he's a legal clerk/Crown Prosecution solicitor/police officer outraged at the decision of the CPS not to prosecute.

They make a stunning offer; I will hand over the CPS file so your journalists can study the evidence and make your own inquiries. But there's a catch - they insist "this is dangerous for me, so if you publish anything I want £1,000 in cash."

The news editor/editor would have agreed to the bargain in a shot. And, with the newspaper bar set a good deal lower than the judicial one, reporters would have used that leaked information to go back to the victims, heard their harrowing story, weighed the evidence and, I am sure, decided to adopt the old adage; publish and be damned.

Just like the Daily Mail did when the police failed in their initial bid to convict the killers of Stephen Lawrence.

Once the bubble had burst hundreds of other victims would have come forward - just as they did with the ITV expose - and hopefully that would have led to Sir Jimmy ending his days doing up to 15 years in jail for being a rampant paedophile rather than meeting his maker as Saint Jimmy.

And yet...

Had the Sun paid £1,000 to that state official the reporters and executives involved would disgracefully be facing carloads of police knocking on the door at 6am and being arrested in front of their families under something called the 1906 Prevention of Corruption Act which carries a maximum sentence of 10 years.

It is that same act which has led to 21 national newspaper reporters and executives being arrested in the last year. Simply for doing their job.

No journalist had ever been arrested under the act in the previous 105 years since it was enacted. In fact the act has never appeared in Essential Law for Journalists the ubiquitous legal handbook for those coming into the trade. No QC or in-house lawyer ever mentioned it to me in my 30 year newspaper career.

Under the act there is no public interest defence. So if a nurse calls up to disclose that due to poor care literally hundreds of elderly patients are dying at a Mid-Staffordshire hospital both she and reporter will face jail if she wants £500 for her trouble. And yet that call might have saved 1,600 lives.

Presumably the brave squaddies who took shocking videos to the News of the World in 2006 proving appalling physical abuse of civilians by British soldiers in Iraq risked arrest too if they were paid a few bob for their troubles? I wonder if they'd have made the call if they knew?

How about prison officers sickened by the special treatment enjoyed by notorious criminals like Myra Hindley or Ian Huntley, who decided to expose it but wanted a bit of "danger money" in return?

What if 'Plebgate', which led to the resignation of a senior cabinet minister and sparked a huge confrontation between the Police Federation and the government, actually arose from a furious police officer deciding to leak the story but wanted paying for his trouble?

Or is it more likely that those important stories would never have seen light of day if the whistleblower had known he or she faced 6am arrest and jail? Would the journalists have risked the same to investigate? Who loses out? You, the British public.

Sue Akers, a deputy assistant commissioner at Scotland Yard, was allowed to say at the Leveson Inquiry - it went unchallenged so we know where Leveson's coming from - that many of the stories obtained from state officials for cash were tittle tattle and of no public interest.

In fact Ms Akers, who will have retired from the Yard before the trial of any Sun staff starts, should have been only too well aware that many of the stories will be shown to have serious public interest.

So in the Sun today when a phone goes on the Sun newsdesk and the journalists are told a shocking story they then ask the nervous caller a strange question; Are you a state employee? Because if you are, no matter how big or important your story is, we cannot listen to you or pay you money for your information because both of us stand a healthy chance of being arrested.

And so instead of beginning to investigate a major scandal the connection is broken and the frustrated journalists sit back and wait for the next X Factor handout or government announcement.

Meanwhile, the Jimmy Savile's of this world will go free while those wanting to expose them face going to jail. It's barmy and its wrong.