The wife of a retired ambassador, she has risen without fuss to the highest rank held by a woman in the civil service.
The pivotal position of European affairs has put Geraldine Byrne-Nason, the second secretary general at the Department of the Taoiseach, at the heart of the action.
When the historic EU bank debt deal was struck in Brussels 10 days ago, she was one of two Irish civil servants in the room in Brussels where the text of the agreement was put together by EU officials for their political masters -- which saw Ireland specifically referenced.
Although Taoiseach Enda Kenny obviously got the public credit for pushing for the deal, the role of Jim O'Brien from the Department of Finance and Ms Byrne-Nason was acknowledged in government circles in the aftermath.
"When they went into the meeting of Sherpas (the EU nickname for the representative of heads of government) and finance guys, they were excellent," a minister said.
Dubliner Mr O'Brien, the second secretary general in Finance and head of EU division, will be by Finance Minister Michael Noonan's side as he seeks to tease out the detail of the deal over the coming months.
The 54-year-old O'Brien is held in high esteem in the Coalition, which is no mean feat considering its appetite for clearing out the upper echelons in Merrion Street when it came to power.
"I think he's brilliant. Jim is politically astute, reads it well and networks. Of all the civil servants I have seen, he is right up there," a minister said.
Aside from the debt deal, with Ireland taking over the EU presidency in the first half of next year Ms Byrne-Nason will also be travelling over and back on a regular basis to Brussels -- a city she is well acquainted with.
When the new Government took up office 18 months ago, she was Ireland's deputy ambassador to the EU.
Tanaiste Eamon Gilmore's desire for more central role in Government Buildings and greater co-ordination of EU and economic policy resulted in the creation of a second secretary general's position in the Department of the Taoiseach.
The job entails co-ordinating the EU end, running the office of the Tanaiste and the Economic Management Council, the powerful mini-cabinet where economic and budgetary issues are thrashed out by the Taoiseach, Tanaiste, Mr Noonan and Public Spending Minister Brendan Howlin.
Although more senior figures applied for the position, Ms Byrne-Nason "impressed" in her pitch for the job, a government source pointed out.
"She's very highly thought of by everyone -- particularly by women. She gets a lot of respect. She's capable, but there's a humanity there. She would bring people with her," the source said.
Certainly held in high regard by the Tanaiste, this closeness has resulted in some sniping from the Fine Gael side that her role involves "chasing after Gilmore" and being too conservative.
Nonetheless, a Fine Gael minister who is taken with her performance describes her as "the best diplomat I've met".
"You wouldn't mess about with her and Kenny gets on very well with her. I find her absolutely excellent," another cabinet member said.
Her no-nonsense nature came out during an incident with a minister earlier this year who wanted to make an announcement ahead of Mr Kenny.
Ms Byrne-Nason reportedly rang the minister up, pointed out that the Taoiseach was taking care of it and reminded the minister of the importance of the pecking order.
Ministers were also happy with her ability to brief them daily -- in a non-political way -- about European developments during the EU fiscal treaty referendum.
The EU presidency will put her centre stage for the coming year.
In a speech delivered three months ago, she spoke of how "the gloss" had gone off Ireland in Brussels following the economic collapse, but the presidency would give the country a chance to make a positive impression again.
Originally from Drogheda, she was one of three children from a conventional middle class family.
The two became close friends and Ms Byrne-Nason was a bridesmaid at Ms Hanafin's wedding to barrister Eamon Leahy, who passed away nine years ago.
"She's the most exceptionally talented woman I know, but carries it lightly," Ms Hanafin said.
Ms Byrne-Nason married fellow diplomat, Brian Nason, in 1989 -- both had been based on opposite sides of the US.
Frequently within the Department of Foreign Affairs, when two diplomats get married, the wife resigns, but a juggling of positions meant the new couple were posted in the same cities, yet never in the same building.
They have one son, 11-year-old Alex, and live on the southside of Dublin.
After his final posting of a distinguished career as Irish Ambassador to Belgium, Mr Nason retired two years ago.
Taking up the role of second secretary general of the Department of the Taoiseach makes Ms Byrne-Nason the highest ranking female civil servant in the country -- and the first to be appointed to a top job on Merrion Street.