A timeline:

January 2006:

Sergeant Maurice McCabe made a complaint about a colleague which led to the officer being disciplined.

December 2006:

A girl made a complaint about Sgt McCabe. In the complaint she alleged he had tickled and behaved inappropriately towards her while she played hide and seek with his children a decade earlier. A file was sent to the Director of Public Prosecutions in which gardaí said there was no grounds for prosecution.

2008:

Sgt Maurice McCabe attends a meeting with in Mullingar, Co Westmeath where he raises concerns about Garda malpractice. He secretly records the meeting.

2012:

Sgt McCabe steps into the public spotlight becoming the most high-profile whistleblower in the force after raising concerns about the internal handling of an assault allegation. A few months later, he lifted the lid on the penalty points controversy, claiming well- known personalities had their points wiped.

2013:

The C&AG publishes a report into the penalty points scandal which backs up claims made by whistleblowers including Sgt McCabe. However, then justice minister Alan Shatter alleges in the Dáil that the whistleblowers didn’t co-operate with the Garda investigation. This is denied.

January 2014:

Garda Commissioner Martin Callinan tells the Public Accounts Committee that only two officers out of a force of 13,000 are making allegations. He says that “on a personal level” he thinks it is “quite disgusting”.

February 2014:

An inquiry led by barrister Séan Guerin is set up in to review the penalty dossier supplied by whistleblowers.

March 2014:

Leo Varadkar, as Minister for Transport, calls on Martin Callinan to withdraw his “disgusting” comment. Days later Callinan steps down amid a separate controversy over the taping of phonecalls at garda stations. Noirin O’Sullivan takes over as acting Commissioner. Meanwhile Mr Shatter apologises to the whistleblowers for saying they hadn’t co-operated with the original penalty points inquiry.

May 2014:

Sean Guerin’s report says Mr Shatter failed to properly investigate matters raised by Sgt McCabe. The minister disputes the findings but stands down. Frances Fitzgerald moves to the Department of Justice. She promises an “new era of policing”.

November 2014:

Noirin O’Sullivan is appointed Garda Commissioner.

February 2015:

The Government sets up the O’Higgins commission of investigation to probe accusations made by Sgt McCabe of garda malpractice in Cavan/Monaghan.

May 2015:

An email is sent to Frances Fitzgerald highlighting a row between legal teams for the Garda Commissioner and Maurice McCabe. No action is taken by the minister and she now says she doesn’t remember the email.

December 2015:

An error on the part of Tusla leads a child protection social worker to write to Maurice McCabe informing him an investigation was taking place into allegations he had sexually abused a child. A claim of digital penetration is cited.

April 2016:

The O’Higgins Report is given in to the Department of Justice. It is sent to the Attorney General for review before publication.

May 2016:

Leaked extracts from the O’Higgins report show Shatter and Callinan handled McCabe’s complaints in an appropriate manner “at all times”.

May 2016:

Days after the O’Higgins report is formally published further leaks reveal that Ms O’Sullivan’s legal team had a strategy of attacking Sgt McCabe’s motivation and integrity during the inquiry. As controversy engulfs the Government, the Commissioner issues a statement saying she never regarded Sgt McCabe as malicious. She points to the 2008 meeting at which it is claimed Sgt McCabe had expressed a grudge towards a senior officer. Sgt McCabe produces his recording to disprove this claim.

June 2016:

Tulsa writes to Sgt McCabe confirming that no allegation of digital penetration has been made against him. Sgt McCabe requested of Tusla all copies of records made on him and his family be released to him.

January 2017:

Children's Minister Katherine Zappone's private secretary phones Maurice McCabe's wife on foot of inquiries she made to the Department of Health. The minister meets Sgt McCabe.

February 2017:

Cabinet sets up a Charleton Commission of Investigation into an alleged smear campaign against Sgt McCabe. Labour leader Brendan Howlin alleges Garda Commissioner Nóirín O'Sullivan was directly involved in a smear campaign - but the Government continues to stand by her.

June 2017:

Charlie Flanagan is appointed Justice Minister by Leo Varadkar. Ms Fitzgerald retains her position as Tánaiste and becomes Enterprise Minister.

September 2017:

Noirin O’Sullivan steps down as Garda Commissioner citing the "unending cycle" of investigations, including the Charleton Tribunal. Her stewardship had also been plagued by separate controversies over fake breath-tests.

November 2017:

Labour TD Alan Kelly asks a series of questions suggesting the Department of Justice knew in advance about the strategy to discredit Sgt McCabe at the O’Higgins inquiry. Focus turns to when Frances Fitzgerald knew about the strategy. Taoiseach Leo Varadkar tells the Dáil she found out around the same time it came into the public domain in May 2016. However, it then emerges that an email alerting Ms Fitzgerald to “a clash” which occurred between the two legal teams at the O’Higgins Commission was sent a year earlier . The Tánaiste says she can’t recall the email and denies any wrongdoing.

Online Editors