How does a reporter get a scoop? Nurturing contacts, wearing out shoe leather, poring over documents. And for some, the toolkit may include phone hacking, honeytraps and covert recording.
When the News of the World's royal reporter Clive Goodman was jailed in 2007 for illegally hacking into royals' mobile phones, his bosses emphasised that this was a one-off.
The Sunday tabloid is a past winner of Newspaper of the Year awards
But the Guardian says such tactics are common at the Sunday tabloid, and claims its journalists routinely employ private investigators to hack into the mobile phone voicemails of hundreds of politicians, celebrities and sportspeople. It also claims reporters on other papers, among them the Daily Mail and the Observer, employ private investigators to obtain information about private phone numbers and addresses.
For the tabloids, and sometimes the broadsheets too, have long used various tricks to find a fact or uncover a story.
And for some, these dark arts - dressing up, following people, eavesdropping, fibbing - add a frisson of John Grisham-style excitement to the job.
A former reporter on one of the red-top papers - who wishes to remain anonymous - says it can certainly be thrilling.
He followed public figures for days on end, eavesdropped on their conversations, even booked himself into adjacent hotel rooms. "There was a thrill, of course. It felt dangerous. You could be sniffed out at any moment."
He remembers how 10 years ago, tabloid reporters paid for the illegally obtained phone bills of the famous, in order to see who they were talking to - an early, lower-technology version of hacking into their phones.
"But then I thought: what am I doing? I didn't get into journalism for this. It started to get silly."
Tessa Mayes, who has worked as an investigative journalist for newspapers and TV shows, says editors have asked her to flirt to win someone's confidence, lie in order to penetrate the inner sanctum of a drugs gang, and fake documents in order to get work in a company under investigation. She has also worked undercover as a receptionist in a brothel.
"If I had said no, I wouldn't have got to work on those stories. It's not unknown for journalists to sleep with their sources in order to meet a deadline. As it happens I haven't needed or wanted to do that."
Sting in the tale
Laurie Manifold, a former investigations editor for the People who is described by media commentator Roy Greenslade as "the father of modern popular paper investigative journalism", pioneered the use of subterfuge in the 1960s and 70s.
Kenneth Drury appearing at Bow Street Magistrates court
He trained his reporters in covert tape-recording techniques and would even set up fake companies to carry out stings.
One of Manifold's most famous stories was the revelation in 1972 that the then head of the Flying Squad, Commander Kenneth Drury, had been on holiday with a pornographer. The story ballooned and led to revelations of corruption in the police force. Ninety officers were suspended and 13 were convicted of offences.
One of the most frequently employed dark arts is the sting, where a reporter assumes a fake identity in order to coax or cajole a public figure into saying something interesting or incriminating.
The most famous is the News of the World's own "fake sheikh", Mazher Mahmood, its investigations editor. He has regularly posed as a member of the House of Saud, donning a white robe and Rolex watch to meet public figures and secretly record what they say.
Over the past 10 years he has taken in Sophie Wessex (who described Cherie Blair as "horrid" and Gordon Brown's Budget as "a load of pap"), Princess Michael of Kent (who labelled Princess Diana "nasty" and "strange"), and Newcastle United chiefs Freddy Shepherd and Douglas Hall (who described footballer Alan Shearer as "boring").
He also claims to have brought 232 criminals to justice - including arms dealers and immigration racketeers - by conning them with his disguise.
In 2003, Daily Mirror reporter Ryan Parry used false references to get a job as a footman in Buckingham Palace. His aim was to uncover security lapses at the Palace in the run-up to President George W Bush's visit.
He revealed details of the President's bedroom as well as the Queen's breakfast habits. Eventually the Queen won a court order preventing the Mirror from revealing any more.
Rebekah Wade is soon to become a News International executive
And it is widely claimed that in 1994 Rebekah Wade - then a News of the World reporter, now editor of the Sun - dressed as a cleaner and hid in a toilet for two hours in order to nab an early copy of the Sunday Times.
The Sunday Times, housed in the same building as the News of the World, was serialising a biography of Prince Charles, and NoTW editor Piers Morgan wanted to know what it said. John Witherow, editor of the Sunday Times, is alleged to have shouted at Morgan: "Theft isn't journalism."
In the late 1990s and early 2000s, a character call "Benji the Binman" - real name: Benjamin Pell - would scour the bins of the rich and famous for anything interesting that a newspaper might buy. He caused a storm with Elton John's flower receipts. In 2000 Philip Gould, Tony Blair's then pollster, suspected Benji of obtaining his discarded memos for papers such as the Times and the Sunday Times.
Are such dark arts - whether illegal or not - justified? "These were important stories, so it was worth it," says Tessa Mayes. "Investigative journalists sometimes need to break the rules, and even the law, in order to get a good story.
"We are not above the law and can go to prison. But even the law recognises journalists can have a public interest defence to justify their methods in certain situations."