The Government has failed in a Court of Appeal bid to block disclosure of the contents of a diary kept by former health secretary Andrew Lansley.
The ground-breaking case marks the first time the courts have considered the public right to see entries contained in a ministerial diary under the Freedom of Information Act 2000.
Transparency campaigners say the case is of importance because the diary covers the time Mr Lansley was working on the Health and Social Care Act and allegedly subjected to extensive lobbying by private healthcare interests.
A journalist, Simon Lewis, made a request to the Department of Health (DH) under the Freedom of Information Act 2000 (FOIA) to see diary contents for the period May 12 2010 to April 30 2011.
Only a redacted version was produced but in March 2013 the Information Commissioner required the department to disclose the majority of the withheld information.
The Government has now lost a series of legal challenges to the commissioner's decision, ending in a unanimous three-judge appeal ruling on Wednesday in favour of disclosure.
It was handed down by Sir Terence Etherton, Master of the Rolls, sitting with Lady Justice Black and Lord Justice Davis.
In the lead ruling, Sir Terence said the FOIA created a general right of access to information held by public authorities but allowed for exemptions from disclosure.
The Government attacked a decision of the FTT - the First-tier Tribunal (General Regulatory Chamber - Information Rights) allowing disclosure of the Lansley diary which was upheld by the Upper Tribunal (Administrative Appeals Chamber).
Government lawyers argued the tribunals were wrong to find the relevant balancing exercise between disclosure and non-disclosure came down in favour of disclosure.
Sir Alex Allan, a former chairman of the Joint Intelligence Committee, had been among Government witnesses who gave evidence that disclosure "would not assist the understanding of the processes of government and would be liable to mislead and misinform the public as to the efficiency and extent of the work of the minister".
Dismissing the Government appeal, Sir Terence said the FTT "actually identified 11 particular types of benefit from disclosure", including "general value of openness" and "transparency in public administration".
The judge also rejected the Government claim that the Department of Health did not hold the diary information "for the purposes of the FOIA".
He declared that while Mr Lansley was a minister in the department the diary entries "were held by the department for itself even if they were also held - in the case of personal and constituency matters - for Mr Lansley as well".
The judge added: "I cannot see that the termination of Mr Lansley's ministerial position made any difference to that position.
"In particular it seems to me clear that it remained relevant or potentially relevant to the department to know, as a matter of historical record, where Mr Lansley had been and with whom on particular occasions, should there be a political, journalistic or historical interest raised with the department in relation to those matters."
Lady Justice Black and Lord Justice Davis both agreed.