Landmark case: eventually Clive Ponting walked free
It is the latest in a line of high-profile cases in which the government's will has been thwarted.
Clive Ponting
The 1985 Ponting case was in some ways the landmark Official Secrets case. Clive Ponting, who had worked at the Ministry of Defence, walked free from court after a jury cleared him of breaking the Official Secrets Act.
It was hailed as a victory for the jury system. The judge had indicated that the jury should convict him.
Ponting had been charged with leaking an internal MoD document concerning the General Belgrano, the Argentinian cruiser which British forces sank during the 1982 Falklands War, killing 360 people.
The government line had been that the Belgrano was threatening British lives when it was sunk. But the document leaked by Ponting indicated it was sailing out of the exclusion zone. Its publication was a huge embarrassment for Lady Thatcher's government.
Cathy Massiter
The Official Secrets Act was drawn into further controversy in 1985. Former MI5 officer Cathy Massiter told a Channel 4 television documentary that MI5 had been illegally bugging the telephones of politicians, human rights campaigners, and pressure groups like the Campaign for Nuclear Disarmament.
Peter Wright and Spycatcher
The high water mark of Lady Thatcher's Official Secrets' battle came in 1987 with the publication of Spycatcher by former MI5 officer Peter Wright.
The book alleged that in the 1960s, MI5 conspired to discredit Labour prime minister Harold Wilson.
Lady Thatcher's government said Wright owed a life-long duty of confidentiality. However, Wright published his book in America and Australia, and despite the government's best efforts, copies came into the UK.
Wright, by this stage an old man, was living in Australia. There was another lengthy and high-profile court battle as the UK Government tried unsuccessfully to extradite him.
However, a House of Lords judgement in 1988 overturned a blanket injunction across all media outlets from reporting anything from former intelligence officers.
The Law Lords criticised the government's handling of the issue, which had cost an estimated £3m.
Lord Goff said: "In a free society, there is a continuing public interest that the workings of government should be open to scrutiny and criticism."
The European Court of Human Rights later held that the UK's actions had violated the right to freedom of speech.
In a neat historical detail, David Shayler - then editor of the Durham University student newspaper - also published some of Wright's allegations.
Richard Tomlinson
Former MI6 officer Richard Tomlinson was sentenced to a year in prison in 1997 for passing secrets to an Australian publisher.
He was released after six months and went to his native New Zealand.
Earlier this year he was arrested in Paris with David Shayler, but was released because of insufficient evidence.
An injunction was placed on Tomlinson preventing him from further breaching the Act. He says he intends to write a book on MI6 which would be a "much better read than Spycatcher".
Sarah Tisdall
However a rare success for government enforcement of the Official Secrets Act was the conviction of Sarah Tisdall. The young Foreign Office clerk leaked to The Guardian newspaper details of when controversial American cruise missiles would be arriving on British soil.
She was found guilty and sentenced to six months, although she only served three.