It is now over 10 years since the start of the long and winding road that may, even now, lead to Damian Green’s resignation as first secretary of state, effectively the deputy prime minister. At the outset, the issues in the case were politically sensitive. The Conservatives, then in opposition, were receiving leaked documents from inside the Home Office. Some of these came from the office safe of the then home secretary, Labour’s Jacqui Smith. Christopher Galley, a civil servant, was suspected of copying the documents to the shadow immigration minister, Mr Green. The cabinet secretary called in the Metropolitan police in October 2008 and the police raided Mr Green’s home and his Commons office the following month, holding him for nine hours, confiscating his phone and going through his computers.

The arrests rightly caused a massive row. No MP had ever been arrested or had their office searched by police in a leak inquiry. The case trespassed on parliamentary privileges in place ever since Charles I attempted to arrest a group of MPs in 1642. David Cameron condemned the search as Stalinesque. Mr Green said that it was his job to criticise government immigration policy and “that’s precisely what I was doing in this case”. In April 2009, the then director of public prosecutions, Keir Starmer, decided that there was “insufficient evidence for a realistic prospect of conviction” against Mr Galley or Mr Green and said he had taken his decision in part because the leaked information did not damage national security.

Fast forward now to last month, when the former Met assistant commissioner Bob Quick told a Sunday Times journalist that one of Mr Green’s office computers in the 2008 search contained pornographic material. Mr Green responded that the claims were “completely untrue” and were “false, disreputable political smears from a discredited police officer”. On Friday a second former police officer, Neil Lewis, repeated the accusations to the BBC. This provoked several senior Tories, including David Davis (who until shortly before the 2008 search had been shadow home secretary) to rally behind Mr Green. Meanwhile the claims are being investigated by the Cabinet Office’s propriety and ethics chief, Sue Gray, as part of a wider inquiry into allegations against the first secretary; her report is expected shortly.

Nine years on, the 2008 raid still festers. Mr Green still bears a raw and understandable grudge against the police search and those who authorised it. His bitterness is amply reciprocated by former police, who feel Mr Green is not telling the truth and is out to get them. Over the years the issues have become tangled up in Tory party politics, in relations between the Met and politicians, in arguments about the press and privacy, including the Leveson inquiry, and now in public concerns about Commons culture. It isn’t just Mr Green who is now more prominent than in 2008. Several others with roles in the original saga, including Mr Davis, Boris Johnson, Sir Keir Starmer and Cressida Dick, now have bigger responsibilities.

The Green case is a murky confluence of principles which all matter, though they can sometimes conflict. These include: the defence of parliament’s special privileges, the right of MPs to hold leaked information, the need for leak inquiries to be proportionate to genuine harm, the obligations on police to observe confidentiality and to stay out of politics, the inappropriateness of pornography both in the workplace and in general, and the protection of privacy in matters of sexuality where no illegality is involved. None of these issues, moreover, can be wholly separated from the constant contest for political advantage within and between political parties. In the end, though, the outcome of the Green affair seems likely to come down, and should, to an even more basic principle – which of Mr Green and his accusers is telling the truth? – and to an even more important judgment: which of them should be believed?