Dramatic events are coming so fast in Northern Ireland, it's sometimes hard to keep up. But one recent development at Stormont deserves to be recorded as a journalistic landmark.

When the Democratic Unionist Party assembly member Ian Paisley Jnr stood down from his father's department last month, he became the first government minister in the UK to resign because of the Freedom of Information Act (FOI). His resignation has since become part of a bigger story: it undoubtedly helped weaken Ian Paisley senior, who has now set his own departure date as First Minister.

Some day, an enterprising media-studies student will produce an acclaimed PhD thesis on the slow demise of the younger of the two Paisleys. His resignation came after relentless revelations over links to the developer and DUP member Seymour Sweeney. Mr Paisley Jnr, it should be stressed, has firmly denied any wrongdoing.

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He did not help himself at the outset of the controversy by appearing to play down his Sweeney connections, telling an interviewer last September: "I know of him, yes". At this point, the businessman was poised to get the go-ahead for a contentious visitor-centre development above the Giant's Causeway, Northern Ireland's only Unesco world heritage site.

FOI disclosures revealed the extent of lobbying by Mr Paisley Jnr in support of this scheme over a number of years. His father had been involved, too – protesting in writing to the Heritage Lottery Fund in 2003 at a grant refusal for Mr Sweeney.

This letter, released last October under FOI, incorrectly claimed the Causeway project had the approval of Unesco itself. When the letter became public, the First Minister reacted with an outburst from the Assembly floor, attacking "wide ranging" FOI requests being "sent in by lazy journalists, who will not do any work". A complaint about his Heritage Lottery Fund letter was made to the Commons Standards Commissioner.

The "cronyism" row over Sweeney proved a headache for another DUP minister, who was poised to issue planning approval for the Causeway centre scheme. She maintained that she had been unaware that the Paisleys had been batting for the businessman. In the end, planning permission was refused.

By this time, it had been revealed – again through FOI requests – that Mr Paisley Jnr had also lobbied in support of a massive government land sale plan, involving Mr Sweeney.

Freedom of Information disclosures did not just come about through journalistic efforts. The hardline Unionist MEP Jim Allister obtained documents showing that Mr Paisley Jnr had lobbied on Sweeney-related projects at the 2006 St Andrews talks that led to the return of the Northern Ireland Assembly the following year. The St Andrews "shopping list" was personally considered by Tony Blair, who was no doubt keen to keep the Paisleys sweet, amid hopes of a power-sharing deal.

The Blair lobbying revelation infuriated other parts of the DUP. The end for Paisley Jnr came through a general FOI request about rental expenses for politicians' constituency offices. It's the kind of enquiry a reporter might submit on a quiet afternoon. But when the draft figures were circulated in the Stormont assembly for checking purposes prior to release, they started alarm bells ringing in the DUP.

That was because the rent received by the two Paisleys for their sizeable joint office was more than three times the amount of the next highest claim. It was then confirmed that Seymour Sweeney had facilitated the mortgage for the purchase of the building, and that the firm owning it was headed by Mr Paisley Jnr's father-in-law.

All within the Assembly rules, but party colleagues had had more than enough of the negative headlines by now. Paisley Junior quit – thanks to "lazy journalists" and that pesky FOI Act.