Numerous options for the relief of overcrowding in Leinster House were considered prior to the Government approving the latest plan to build a major extension just north of this highly-sensitive historic building.
At one stage it was planned to transform the west block of Agriculture House on Kildare Street - due to be evacuated by civil servants relocating to Wexford - into overflow offices for Dail deputies, with the top floor raised to provide double-height committee rooms.
Dublin architects de Blacam and Meagher came up with a scheme to provide a new building at the rear of Kildare Place, linking Agriculture House with Leinster House, but this option proved to be "wildly expensive" and was pigeonholed as a result.
In any case, the idea of recycling Agriculture House did not appeal to TDs. Many of them believe it is too far removed from the "centre of action" around the Dail; they would also have to bear in mind the length of time it takes to respond to the division bell.
Although Leinster House obviously exercises "eminent domain" over other buildings in the vicinity, one of the key constraints on its expansion is that every TD has just eight minutes to get to the Dail chamber after the division bell first rings out.
Mr David Byers, assistant principal architect at the OPW, said that when he became involved in designing the £17.5 million refurbishment of Government Buildings he had to ensure that the Taoiseach's office also met this time constraint.
The advantage of building a new link between Leinster House and Agriculture House, to the rear of Government Buildings, is that it would replace the hideous concrete brick wall which runs into the newly-restored southern facade of the National Museum.
Mr Barry Murphy, the OPW's chairman, said yesterday that this wall - which everyone agrees is offensive - would "definitely go" in the long term because the former Fisheries Yard behind it, where turf for Leinster House used to be stored, was a potential future landbank.
Entrenched political positions also stand in the way of redeveloping the Fisheries Yard. Right beside it is the 1936 building which has been used for years by Labour Party deputies, and they are very committed to staying there. Equally, the OPW has no plans to move them out.
Another consideration, according to Ms Angela Rolfe, one of the OPW's senior architects, is that developing the Fisheries Yard would move the centre of gravity of the whole complex to the south, away from Leinster House, whereas the College of Art site is seen as more proximate.
But what clinched the decision to proceed with a major extension on the site now chosen was money. The OPW simply could not secure sufficient funding to redevelop both this site and the Fisheries Yard, so a choice had to be made within the approved budget of £25 million. Given that the Government only approved the allocation last Thursday, design work has yet to start on the proposed extension, which - as Mr Murphy pointed out - will be the OPW's "first public building project, in a ceremonial sense, for the Oireachtas since 1922".
Although it is exempt from the normal planning process, the building will require an exceptionally sensitive design, as it will rise up behind the curved screen wall to the north of Leinster House, on its Merrion Square front, and will be seen from the square and from Kildare Street.
It would not, of course, be the first building to encroach on what was once the parkland around the Duke of Leinster's former town house. After all, the National Gallery, Natural History Museum, National Library and National Museum were all built there in the 19th century.
If An Bord Pleanala sanctions the National Gallery's current plan for a £12.5 million extension into Clare Street, the OPW's architects might even be able to argue that the latest extension to Leinster House would help to obscure views of its controversial tower from Merrion Square.
One of the major design issues is whether to build directly over the curved screen, as was done in the Rotunda Hospital, which, like Leinster House, was designed by Richard Castle. However, it is probable that the extension will be set back from this single-storey wall. The height of the new building will reach the eaves of Leinster House and the National Gallery, its two closest companions. According to Mr Byers, the building is likely to be "very plain" and clad in stone, as a fully-glazed facade would have a "glittering effect" viewed from the square.
Care will also have to be taken to ensure that it does not block too much daylight from the three bow windows of the Seanad chamber. The new building would not be linked with Leinster House at every level; its main access is to be on the ground floor, on either side of the Oireachtas Library.
At almost 90,000 square feet, Mr Byers concedes that it will be a "massive building." The real challenge is to make sure that it does not overpower the existing architectural ensemble around what one person described as the "People's Republic of Leinster House".