He achieved much more, of far more personal importance, in his work and family lives but he will probably be remembered as the man who brought down Bertie Ahern and Padraig Flynn.
He was of the generation in the 1950s who took the boat to England, although, unlike most others, he actually had prospects at home. He left the family farm in Lislarry, Co Sligo, despite the chance of a promising career in the civil service.
In London, he worked in engineering before getting involved in property development and settling in Luton. He made good, accumulating considerable wealth through astute investments and hard work.
Then, in the late 1980s, his thoughts turned back across the Irish Sea. In Dublin, he scouted for potential developments, but found what he would later describe as “roadblocks” everywhere he turned. These roadblocks were manned principally by the late Liam Lawlor and Lawlor’s chum, the former Dublin city manager, George Redmond. Their main concern was to have their respective palms greased.
During evidence at the planning tribunal, Gilmartin recalled being told at one stage that Lawlor was a consultant, to which he replied: “I wouldn’t have that man consulting on a shithouse.”
According to Gilmartin, that pair were to the fore in demanding backhanders from him, but they weren’t the only ones.
One proposal for Bachelor’s Quay in Dublin City centre went nowhere, and then he struck on the ideal of a major shopping centre on the M50. He was the first to spot the potential for the site that became the Liffey Valley Shopping Centre.
He was taken by the local bigwig, Bertie Ahern, whom he initially believed to be “a straight man who wouldn’t see me wrong”. But Ahern was neither able nor willing to help him get past the sweaty palms.
On the surface, Gilmartin was feted by politicians who viewed him as an immigrant returning with stuffed pockets. He was brought into Leinster House to meet the cabinet in a famous gathering in 1989 that nobody but Mary O’Rourke could recall.
According to Gilmartin, after he left the room he was approached by a gent who handed him a piece of paper with a long number written on it. He said he was told to deposit £5m in it. His reply to the request was succinct: “You so-and-sos make the mafia look like monks.”
That same year, he handed Padraig Flynn a cheque for £50,000, believing it was a donation to the party to clear the roadblocks. Flynn trousered the money.
Gilmartin ran into financial difficulty and brought Owen O’Callaghan on board. The two fell out, and O’Callaghan eventually took over the whole project. Eventually, Gilmartin returned to the UK, vowing never to do business in this country again.
Within 10 years, the planning tribunal was established, upturning stones and finding all manner of maggots crawling out. Gilmartin’s name came up and he was contacted but he didn’t want to get involved.
Then, in 1998, sitting at home in Luton, he saw Padraig Flynn on The Late, Late Show trying to disparage him.
“He’s a Sligo man who went to England and made a lot of money,” Flynn told Gay Byrne.
“Came back. Wanted to do a lot of business in Ireland. Didn’t work out for him. He’s not well. His wife isn’t well. He’s out of sorts.”
That was the final straw for Gilmartin. He changed his mind and agreed to co-operate.
He gave evidence at the tribunal under serious pressure from a whole array of lawyers representing the great and the good of Irish business and politics of the time, but he held tough.
His allegations were numerous and directed at a whole variety of parties, but at least some of them were backed up with relatively solid circumstantial evidence.
Flynn’s grabbing was exposed, but the real damage was done in an allegation Gilmartin made against Ahern. He told the tribunal that, in 1992, O’Callaghan had told him that he had given Ahern sums of £50,000 and £30,000, the latter payment to allegedly block a tax break for a rival development.
That allegations led to the investigation into Ahern’s finances, and the rest is well trod history.
Gilmartin moved to Cork about 10 years ago and initially concerned himself principally with caring for his wife, who had a long-term illness.
He certainly left his mark on the Irish psyche, ranking perhaps just below his fellow tribunal witness James Gogarty as an outsider who managed to blow the insider world of corruption sky-high. Whatever his motive, he did the State some service.
The tragedy of Gilmartin’s attempts to develop sites in Dublin is that he was a man out of time. If he had been returning a decade later, the city was primed for such development.
As it was, he was a visionary, dreaming two steps ahead of the imagination of those in power. He was, like others before him, among the ranks of the pioneers, rather than the settlers who followed, to reap the benefits of his vision.