THE former chair of Stormont's Finance committee, Daithí McKay arranged a Sinn Féin back channel to loyalist Jamie Bryson to 'coach' him ahead of his appearance in front of a committee investigating the Nama property scandal.

The correspondence, seen by the Irish News, has been described as "political dynamite" by the Ulster Unionist Party which has called for an investigation.

Mr Bryson made numerous allegations about political corruption linked to the £1.2 billion sale of property in Northern Ireland, owned by the Republic's so called bad debt bank, Nama.

Known as Project Eagle, approximately 850 properties, with borrowers originating from Northern Ireland, were sold to American company Cerberus after the 2008 property crash.

There were allegations of a £7 million 'kick back' for businessmen, legal professionals and a senior political figure who helped secure the deal.

During his evidence last September the Co Down loyalist made explosive allegations about 'Person A' throughout his testimony.

At the conclusion of his evidence, Mr Bryson named 'person A' as Peter Robinson at which point his evidence was brought to a close by the committee chair, Mr McKay.

Mr Robinson has always denied he was to benefit financially from the deal, the circumstances of which are currently being investigated by the National Crime Agency.

Documents seen by the Irish News show that the tactic of referring to the DUP leader as 'Person A' until the last minute was suggested by a Sinn Féin party member Thomas O'Hara, whom Mr McKay had put Mr Bryson in touch with.

None of the documents seen by the Irish News give any indication that Nama related information leaked to Mr Bryson came via Sinn Féin - they do however show 'coaching' and advising on tactics to firstly be allowed to give evidence in public session and secondly to get Peter Robinson named in relation to the property scandal.

At the time relations between Sinn Féin and the DUP were at an all time low.

Read: full Nama coverage

Current Finance Minister Máirtín Ó Muilleoir was a member of the finance committee at the time and the Sinn Féin back channel gives Bryson advice on when he will step in and what questions he will ask during the evidence session.

The Irish News understands copies of private messages, using Twitter direct messages, were leaked after one of those engaged in the communications accessed their iCloud account from a shared computer.

In the days prior to the hearing Mr McKay encouraged the loyalist to send copies of letters he was planning to present to the committee so he could advise him.

In a message on September 17 - six days before the hearing - Mr McKay says in a private message to Mr Bryson: "What should tick the box of the committee for public session in terms of your response and I will be saying this to other witnesses ..."

Another message from the MLA to the whistle blowing loyalist says: "Send me a draft of the letter you are sending. Keen to get you into public session."

The documents suggest Mr McKay had seen documented evidence of the loyalist's evidence to the committee up to 72 hours prior to his appearance.

On September 17, Mr McKay sends the loyalist a message saying "follow @thomasgohara" a Twitter account of Thomas O'Hara, a Sinn Féin party member and North Antrim election worker.

From then on all correspondence seen by the Irish News takes place between Bryson and the Sinn Féin party worker.

However, Mr O'Hara makes clear his connection to the former finance committee chair.

Jamie Bryson watches Sinn Féin MLA Daithí­ McKay and former chair of the Finance Committee in the Great Hall in Stormont before he appeared at the Nama inquiry in September 2015. Picture by Mal McCann

In one message on the day before the hearing, he writes: "Texted Daithí there, he says they will be putting a statement out ahead of the meeting tomorrow sometime. Hold the documents back for now, depending on how he interprets them it could put the frighteners on (John) McCallister (independent MLA)."

On September 22, the day before the committee hearing, there were questions over whether the loyalist would be forced to give evidence in closed session, the Sinn Féin worker messaged him to say; "I'm just trying to establish what Mairtin (Ó Mullieor) or someone can jump upon and say 'there's no way we can turn him away this is credible, relevant and in the public interest'."

"Give serious consideration to giving one piece of your file such as one letter to the committee ahead of the vote. At the moment it could swing against you. What could you give?"

In reply Bryson talks about private emails from some of the key players he has included in his evidence bundle.

Read: full Nama coverage

He also advises Bryson on what he can say before the session gets shut down.

"Daithí only one that can hit the button or tell the clerk to hit the button. But if it gets to the point that the majority of members are pushing him for it he may have to. You have to ensure that it doesn't get to that point.

"If I were you I'd avoid entirely having a go at the Alliance and DUP in your opening statement. That will make it much harder to put pressure on the chair. Have a go at them when it gets to the q and a and when the damage is already done!"

However, the most damning correspondence takes place on September 19, five days before the hearing.

Mr O'Hara messages Bryson saying: "A wee suggestion for your closing paragraph. When talking about Robinson refer to him as 'Person A'. So say all you have to say about him referring to him as Person A. Then in your final line say: person A is Peter Robinson MLA.

"Means the committee cannot interrupt you and means that you don't have to say Robbos name until the very last second. So then it's job done".

When contacted last night Mr Bryson refused to discuss whether he had been advised by Sinn Féin prior to his evidence session saying "I will be seeking legal advice around how these alleged communications were obtained.

"The path to the committee hearing is irrelevant, the evidence provided that should be tested, and I believe that evidence has stood up to robust scrutiny."

UUP MLA Philip Smith who sits on the finance committee said: "If these documents are genuine, the claims within them are political dynamite and would have to be investigated."

Read: full Nama coverage