Nine days out of Liverpool, the 17,540 tonnes SS Lapland finally began to exit the Atlantic Ocean for the calmer waters of New York Bay. Making its way through The Narrows and up the Hudson River, hundreds of passengers percolated to the top deck, to catch a better glimpse of the Statue of Liberty coming into view on the port side. It was a symbol of freedom, a sign the journey was nearing its end. There was cheering then. There always was once the lady of the harbour beckoned.

Manhattan lay off to their right, already steaming in the early morning of 11 June 1919, a shimmering monument to progress in the still-young century. The Singer Building, the Met Life Tower, and, larger than anything they'd ever seen before, the Woolworth, all 55 neo-Gothic storeys of it, rising to meet them. From the soldiers returning from Europe to resume lives interrupted, to the emigrants dreaming their lives anew, the reactions were similar as the skyline took their breath away.

Whooping and hollering

Far below the whooping and the hollering, Eamon de Valera remained hidden in the lamplighter's cabin. This dark, dank room had been his quarters since a pair of Michael Collins's lieutenants had smuggled him aboard back in Liverpool. Rats had gnawed through his spare clothes, brandy had helped him gain his sea legs, and the sailor with whom he shared the tiny space, believed the gaunt stowaway was on the run for murdering two policemen. He wasn't on the run for murder. His life was way more complicated than that.

Since being famously spared execution for his part in the 1916 Easter Rising he'd been imprisoned twice by the British and embarked on a political career. In the December 1918 General Election he was returned in absentia for the constituencies of East Clare and East Mayo. Unable to make the sitting of the first Dáil on 21 January 1919 because he was still languishing in Lincoln Jail, de Valera escaped on 3 February, following a convoluted operation involving the classic cliché of cakes filled with files and keys.

On 1 April, he was elected Priomh Aire of the Dáil, making him de facto leader of a rebel government. The title was meant to denote prime ministerial status but the semantics mattered little out at sea where that Dáil's lack of international recognition was brought home to him every time he lay down in his uncomfortable, temporary billet.

De Valera needed to be in peak condition for his first major public speech of the campaign at Fenway Park. Built by Charles E Logue, a Derry-born contractor, it was home to the Boston Red Sox, who during the 1919 season drew an average of around 6,000 fans to baseball games. Even the day nine months earlier when the team, including Babe Ruth, clinched the World Series, just over 15,000 were present.

For the appearance of de Valera at a public rally organised at less than a week's notice however, it was still expected that maybe 25,000 people might show up come Sunday afternoon, this being the self-styled most Irish town in America, after all. By lunchtime on a perfect summer's day, it became clear that twice that number were going to attend.

In the seven years since it opened for business, Fenway had never hosted anything quite like this. A full hour before the scheduled start of 3pm, police began to block off entrances for fear too many people were pushing their way into the venue. Thousands were already too late and confined to eavesdropping the action from outside; disappointed that they missed a colourful and unique spectacle. Many carried signs voicing their support for Ireland or displeasure with England. 'England is disqualified and unfit to rule Ireland' read the banner from the Boston Gaelic School Society. Everywhere, tricolours and stars and stripes fluttered cheek by jowl.

The unruly crowd was electrified by the sudden sight of three mounted policemen beginning to clear the narrowest pathway to allow de Valera and the welcoming committee to navigate through the multitude. The crowd surged forward from both sides to try to catch a glimpse of their hero. Women fainted in the crush, several appeals were made to try to calm the masses, yet still they pressed forward. Even when de Valera finally reached the stage, men clambered over reporters' tables to get closer to the action.

In a city where politics has always been something of a bloodsport, the line-up of esteemed Bostonian dignitaries alongside him on the stand represented a veritable rogues' gallery.

District Attorney Joseph C Pelletier was already under investigation and would eventually be disbarred for criminal conspiracy. Former Mayor James Curley's nickname 'The Rascal King' only hinted at the corruption and scandal that attended every stage of his political career. Curley's successor, Andrew Peters, was later exposed as a paedophile. As he sat in Fenway that day, he was already sexually involved with a 12-year-old girl.

They weren't the only ones with colourful reputations. Dan Coakley, a prominent lawyer, had earned a fortune by luring extremely wealthy men into compromising positions with prostitutes and getting photographs of the scene.

A high-profile start

In the middle of this motley crew sat de Valera, smiling in most photographs, obviously and inevitably impressed by the enormous show they were staging in his honour. The quality of de Valera and Boland's intelligence about so much else in Irish-America suggests they must have realised they weren't exactly hanging with choirboys. Given the dimensions of this theatrical event he may not have been able to afford to care about the morality of the men behind it. This lavish promotion garnered international headlines and the perfect high-profile start to his trip.

Senator David I Walsh stole the show. The son of Irish emigrants, Walsh was the first Irish Catholic to reach the Senate from Massachusetts and the first to govern the state. One historian described him as possessing a "hatred of perfidious Albion." This was certainly a day when he lived up to that billing.

"As I looked for the first time in the face of that great leader, my mind went back to another great man," said Walsh. 'There was something about that form. There was something about that face. There was something about that intellect. There was something about his cause that made me think of him as I thought of that great American who 57 years ago came into American life and by his strength and leadership broke the shackles of slavery of 3,000,000 black men. So the Lincoln of Ireland will take the shackles of tyranny from the limbs of the sons of Ireland. Thin and lean in stature, angular in form and features, bright and clear in intellect, born in lowly, humble circumstances, you can be the next Lincoln…"

For this sort of rhetoric and a whole lot more about how Ireland's cause should be America's too, Walsh earned enormous applause and piqued the interest of the British secret service. The British began keeping a file on him from that point on. He was exposed as a regular visitor to a gay brothel in Brooklyn in 1942 – an outing that played some part in him losing his Senate seat four years later.

W hen a cablegram reached de Valera in mid-August informing him that Flanagan had finally landed in New York, he assumed this heralded the arrival of Fr Michael O'Flanagan, vice-president of Sinn Féin. The person in question was actually his wife, the former Sinéad Flanagan. Harry Boland, during a trip back to Ireland, had persuaded her to make the trip. She was reluctant to leave her children for that long and, whether she knew it then or not, her husband wasn't exactly thrilled with the idea of her coming either.

"[Boland] said that Dev was very tired and worn out in America and that I should go to see him," said Sinéad de Valera. "The visit to America was one of the biggest mistakes I ever made. Dev himself had nothing to do with my going. He did not know until I arrived. I went in 1920 and travelled on a false passport. Mick Collins carried my trunk out to the car. The outward journey was slow, and I was sick for part of the time. I felt lonely and sad thinking of the children at home."

The couple had been married since 1910, already had six children and yet, due to the vagaries of the struggle, they hadn't lived together as man and wife since May 1918.

Almost immediately upon being reunited, the de Valeras went on holiday together to Greenwich, Connecticut. It was about an hour outside New York, just near enough for him to return, if need arose. Their presence at Edgwood Inns, an exclusive high society retreat, replete with a casino, merited a mention in the Hartford Courant.

It's fair to assume the couple had some serious work to do on their relationship after so long apart. For all his attempts at keeping up correspondence from his various locations over the years, such a prolonged and stressful absence would have placed enormous pressure on any marriage.

Kathleen O'Connell might just be the most under-acknowledged figure in Irish history. From Caherdaniel, Co Kerry, she emigrated to America in 1904 and worked for Cumann na mBan and the Friends of Irish Freedom before being co-opted onto de Valera's staff in 1919. She became his confidant, sounding-board and confessor, possessing, at least, some influence during most of his political career.

She led, as The Irish Times put it memorably at the time of her death, "a life of magnificent unselfishness". For this loyalty then, including lengthy spells on the lam when they both returned to Ireland, her reward has been to have her good name slandered by the recurring speculation that herself and her boss were also lovers. These rumours were so prevalent that de Valera himself addressed them.

Spoken from the pulpit

"It went on not merely from platforms and in private, but it was spoken of from the pulpit; it came from the altar," he said in the Dáil on 22 November 1928. "I myself was told by a lady in Chicago that a Bishop had told her that my wife had to go over to America in order to keep me straight because I was associating with women… The private characters of individuals were the subject of propaganda of that particular type. My wife was supposed to have had to leave the country because she could not live with me. I was supposed to be living with two or three other women. I am taking my own case because I know it."

It is impossible to know whether the smears had any legitimate basis. What can be said for certain however, is that the correspondence between the women betray no evidence of any problems befitting two sides of a love triangle. One letter ends with the words: "love dear Kathleen from your sincere friend, Sinéad de Valera". This is hardly the way a betrayed wife would write to her husband's mistress.

It may be possible to only parse one single phrase communicated between the women, as potentially illustrative of some row between them: "I am sure you must have thought I was a real idiot that day I left Washington," wrote Sinéad de Valera. "I suppose I was a bit tired and therefore extra emotional?"

A reference to some unsightly clash between the pair or merely an excessively teary goodbye? Whatever, this type of imaginative innuendo is hardly enough on which to support any gossip that O'Connell and her husband were paramours.

Extracted with the permission of the publisher the O'Brien Press from 'De Valera in America' by Dave Hannigan, price €14.99/ £11.99 paperback. Available from booksellers
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