Along with the main business, he also inherited a stud farm, a shopping centre, a building society, a builder's providers company, and two small banks.
While it continued to lend to the Gallagher Group, it also operated from an office in his shopping centre in Donaghmede where it received small deposits from local shoppers.
Alongside this, he also had marketing and architectural services, and would take on the development of housing estate amenities including parks and roads.
[2] Gallagher continued the relationship his father had cultivated with the leading planner in Dublin, George Redmond, giving him regular large payments and paying for family holidays.
His developments often ignored conditions laid down by planners, and Gallagher would also fail to provide amenities such as footpaths and green spaces in his housing estates while still charging ground rent to the new homeowners.
The Gallagher Group became notorious for proceeding against and seeking jail sentences for homeowners who did not pay the ground rent due.
Spurred on by the election of a Fianna Fáil government in 1977, and the expansion of the public sector brought in a new surge in demand for office space in Dublin.
The Gallagher Group was instrumental in the demolition of a number of historic buildings in the area's Georgian and Victorian core, and replaced them with unsympathetic, modern office blocks in which he was fiercely opposed by preservationists.
Older buildings that Gallagher owned were often left open to the weather, and there were a number of suspicious accidents that damaged them beyond repair.
Two of the most notable buildings razed were St Ann's School and Molesworth Hall which were designed by Thomas Newenham Deane and Benjamin Woodward.
Architectural students occupied St Ann's School in an attempt to delay its demolition, and Gallagher responded with a press conference announcing that he would lay off 300 workers across the city if the occupation was not ended.
This led to counter demonstration from the construction workers, and ultimately a high court injunction ordering the squatters to be evicted, which Gallagher did forcibly.
The following day, Gallagher was informed by Haughey that he owed over £1 million to Allied Irish Banks and he requested £750,000 be paid towards the debt.
Agreeing to pay £300,000, this transaction was concealing the fact that this was a non-refundable deposit for land which Haughey would later sell to the Gallagher Group in 1984.
[2] Gallagher invested in racehorses, including £4 million in the bloodstock market, and participating in the racing and breeding syndicate at Coolmore.
In an attempt to stimulate cash flow, he built a high-end shopping centre on St Stephen's Green, the Galleria and started on the redevelopment of Phoenix Park racecourse, against the advice of his bankers.
Irish Life Assurance company had indicated it would pay £16 million for the site in 1981 if the outstanding planning and lease problems could be resolved by Gallagher.
Gallagher wrongly assumed he had a legal agreement with Irish Life, and proceeded to buy a 4-acre Earlsfort Terrace site in January 1982 for £9.5 million with plans of selling it to a British institution.
[2] Gallagher struggled to resolve leasing issues with the Slazenger site, making some progress before he was stymied by one tenant with a strong legal case.
Straffan House was repossessed by the banks just 3 weeks after Gallagher had moved in, along with his stud farm, horses worth £2 million, and his Rolls-Royce.
The liquidator's report, released in 1984, showed that the Gallagher family, as well as associates, had accrued more than £250,000 in fictitious loans, and a wider fraud investigation was instigated.
[2] In partnership with his brother Paul, Gallagher attempted to restart his career in property development in 1983, securing finances from small banks.
This was owing to a group of friends, Tony O'Reilly, P. V. Doyle, Byrne, and his uncle Charles, paying Gallagher's living expenses and guaranteeing his loans.
He moved to London in 1984, where he bought flats which he refurbished and sold on, and by 1987 he could afford Balsoon House on 31 acres at Bective, County Meath, where he lived at the weekends.