Changes to the NHS have been described as "so big, they can be seen from space". But, closer to home, the risks posed by the shake-up will not be seen by the public. The government has overruled an Information Tribunal order to publish the NHS "risk register". It is not the first time the ministerial veto has been used:
Health Secretary Andrew Lansley's decision to keep the potential negative consequences of his NHS shake-up secret marks a "step change" in the government's attitude to freedom of information, according to the information watchdog.
The risk register sets out what could happen as a result of the government's health reforms - an early leaked version warned the cost of GP care could rise and that ministers could lose control of the NHS.
Mr Lansley's decision to block a Labour attempt to get the document published is the first time the veto has been used to stop disclosure of a policy document.
Campaigners described the minister's move as "potentially a very worrying development".
"The veto has only ever been used in relation to ministerial decisions," said Maurice Frankel, director of the Campaign for Freedom of Information.
"This is the first extension into other types of information relating to policy formulation."
Mr Frankel said campaigners had strongly opposed allowing ministers a veto in the Freedom of Information Act.
"We had serious concerns that the government was not submitting itself first to appeal and then to court - choosing instead to go for a veto."
But, overruling Information Commissioner Christopher Graham's order to publish the NHS risk register, Mr Lansley told Parliament it was in the "public interest" to keep it secret and protect discussions between ministers and civil servants.
"The public interest is best served... by officials and ministers being able privately to consider such issues, including any risks," he said.
Three years ago, the then Labour Justice Secretary Jack Straw became the first minister to use the veto.
He overruled the Information Commissioner's orders to publish minutes of cabinet discussions in the run-up to the war with Iraq.
And his arguments for doing so were very similar to Mr Lansley's - that publication would "risk serious damage to cabinet government".
Dr Christopher Lamb made the request in December 2006 to see minutes of cabinet meetings held in March 2003, when the legality of going to war with Iraq was discussed.
The Information Commissioner insisted the public interest in revealing the minutes outweighed ministerial concerns about revealing cabinet splits over the war.
But the government appealed and, three years after the request was first made, Mr Straw overruled the commissioner's order to publish.
"He considered the potential dangers to collective responsibility and good government that would arise from disclosure of the minutes to be particularly pressing," according to the then Information Commissioner Richard Thomas.
Timothy Pitt-Payne QC, who investigated whether Mr Straw's decision could be judicially reviewed, described it as a "serious incursion" on freedom of information powers and questioned whether ministers should have a veto at all.
Government policy states that the veto should be used only "in exceptional circumstances" and only after a "collective decision of the cabinet".
And it was Mr Straw who again got cabinet backing in 2009 to block the release of ministers' discussions over Scottish and Welsh devolution.
He argued that keeping cabinet deliberations secret was in the "public interest".
"A lack of confidentiality would result in watered-down discussion and as a result decision-making would be impaired - an outcome which is not in the public interest," Mr Straw said.
Attorney General Dominic Grieve, a Conservative MP, turned down another request to make the same minutes public earlier this year, arguing they were so sensitive that disclosure could harm relations between UK administrations.
Many of the ministers involved are still MPs or peers and disclosure of who said what to whom - even though it was 15 years ago - has the potential to cause embarrassment.
Maurice Frankel said it was still a very sensitive issue in Scotland.
"With the SNP in government and independence high on the agenda, disclosure could well have an impact on active political developments," he added.
What it means
Dr Ben Worthy, of University College London's constitution unit told the BBC: "Politicians don't like surprises and FOI springs surprises on them."
On his blog, Dr Worthy wrote that the fourth ever use of the ministerial veto reflected "growing criticism" of freedom of information from establishment figures.
"The veto gets easier politically the more it is used," he wrote. "As ever [the risk register] case is the 'exception'. However, some feel it sends out the wrong signal and each veto use erodes confidence in the system.
"It also adds to growing criticism of the Act from Gus O'Donnell, Tony Blair and Jack Straw, who called for additional protections for policy-makers."
Criticising the government, information watchdog Christopher Graham said that "none of the criteria for exceptional cases" had been met in NHS risk register case and that, in future, any use of the ministerial veto "should be genuinely exceptional".
Alexandra Runswick of Unlock Democracy said the government should have a "much more enlightened attitude" to disclosure.
"They are within their right to veto publication but it's extremely disappointing. Central government have never liked FOI - they see disclosures as gaffes or embarrassments.
"It takes a long time to change that civil service mindset that it is in the public interest to protect what they're doing. It's a very big culture shift and lots of civil servants aren't used to it."
The top Whitehall official until last year has defended the government's right to keep policy deliberations secret.
Lord O'Donnell said disclosing documents such as the risk register would "reduce their effectiveness" and would have a "chilling effect" on opinion-sharing.
Officials must be candid, frank and not be distracted from their task, he told an Information Tribunal.
The retired mandarin said there was a danger that disclosing risk registers "could harm rather than assist public debate".
And in a recent appearance before the Commons justice committee, Jack Straw said the law should be changed to ensure there was "a space in which decision-makers can think thoughts without the risk of disclosure".
He told MPs officials must be able to give advice without it going public.
So is it in the public interest to give ministers and civil servants the freedom to speak their mind when deciding to go to war, discussing the risks of huge policy changes, or disagreeing with colleagues?
Or, as freedom of information campaigners argue, would the public be better served having sight of how decisions are made and the potential consequences of those decisions - even if this might cause bad headlines?
"It's very hard to separate the two," said the Freedom of Information Campaign's Maurice Frankel. "The more bad headlines there are, the more likely it is there will be an impact on what people in government feel they can say."