After Duncan's win in 1927, the Irish Open was dominated by English golfers for more than a decade. The only non-English winner before the Second World War was the South African Bobby Locke in 1938. Ernest Whitcombe won in 1928 - he opened with 68 and 69 for a seven-stroke lead and held on for a four-stroke victory. The Whitcombe brothers - Ernest, Charles, and Reg - won four of the inter-war Irish Opens between them. Reg, after a playoff loss in 1935, won in 1936 with closing rounds of 68 and 69 for a record total of 281. The event paused for the war and stuttered back to life. There was an Irish Open in 1953, and then nothing until 1975. The lost decades sit awkwardly in the record book - twenty-two years in which the championship that should have anchored the Irish golfing calendar simply did not exist.

Carroll's, the Dublin tobacco company, had sponsored a separate tournament called the Carroll's International at Woodbrook Golf Club since 1963. In 1975, with the European Tour just three years old and looking for a national open in Ireland, Carroll's took over sponsorship of the revived Irish Open and folded the Carroll's International into it. The first revived event was played at Woodbrook in 1975. Christy O'Connor Jnr won, finishing a stroke ahead of Harry Bannerman, and collected first prize of £5,000 - thirty-three times Duncan's purse from 1927. Carroll's stayed on as sponsor through most of the 1980s. The Irish Open became one of the largest galleries on the European Tour, second often only to the BMW PGA Championship at Wentworth.

In 2012, the Irish Open went to Royal Portrush Golf Club on the North Antrim coast. It was the first time a European Tour event had been played in Northern Ireland since the troubles closed the question down. It was the first Irish Open in Northern Ireland since 1953, and the first at Portrush itself since 1947, the year Fred Daly won the Open Championship at Hoylake. The event drew 112,000 spectators over four days - 131,000 across the whole week - the highest attendance ever recorded on the European Tour at that point, and the only time a European Tour event had sold out before play began. Jamie Donaldson won by four strokes. The 2012 Irish Open was, in a quiet way, the proof of concept that allowed the Open Championship itself to come back to Portrush in 2019.

From 2017 to 2020, the Irish Open was one of the European Tour's premium Rolex Series events, each carrying a minimum prize fund of seven million dollars. During those years the championship moved to early July, two weeks before the Open. From 2014 to 2022 (except in 2016) it was part of the Open Qualifying Series - the leading three players in the top ten who had not already qualified earned a place in the Open. Sponsorship has cycled through partners: Nissan to 2006, Adare Manor briefly, 3 Mobile, Fáilte Ireland, Dubai Duty Free in conjunction with Rory McIlroy's foundation, then Horizon Therapeutics from 2022 onwards. Amgen acquired Horizon in October 2023, and the 2024 edition became the Amgen Irish Open. The K Club, the resort in Straffan, County Kildare that hosted the 2006 Ryder Cup, signed a long-term deal in April 2022 to host the Irish Open in 2023, 2025, and 2027.

The Irish Open has a complicated relationship with continuity. It paused for the war years. It paused for the long stretch from 1954 to 1974. It paused around sponsorship and venue and the broader fortunes of Irish golf. But when it works, it works. The 2012 attendance at Portrush. The 2010 and 2011 attendance at Killarney, second only to the BMW PGA at Wentworth. The fact that it remains, by some distance, the most important domestic golfing event of the Irish year - the one McIlroy's foundation cared enough to put its name to, the one that turned the question of whether the Open might come to Portrush from a fantasy into a logistical problem. National opens are easier to start than to keep. Almost a century on, the Irish Open is still here.