Whatever else he did during his long political career, Charles J Haughey will always be given credit for the conversion of Government Buildings. Completed in 1991 at a cost of £18 million, it was his very own grand project, inspired by the more dazzling achievements of Francois Mitterand in embellishing the city of Paris. But just like the British Embassy in Ballsbridge, Government Buildings was left with an unfortunate blot in the foreground - a security hut through which all visitors had to be processed. Though designed by Office of Public Works architects, it was little more than a shed, with a pitched roof, aluminium frame and infill panels.

Not only did this unsophisticated kit create a very poor first impression of the "Chas Mahal", it also sat rather uneasily alongside the new agenda of openness and transparency, embodied in the mid-1990s Strategic Management Initiative. The fact that it was accompanied by a smaller hut for the Army, directly opposite, didn't help.

So when water started leaking into the basement rooms underneath, between the Attorney General's office and the Department of Finance, it became clear that the security huts would have to be demolished to deal with this problem - and senior OPW architect Angela Rolfe seized an opportunity to replace them altogether.

She argued the case for bringing in outsiders, as the OPW itself was perhaps carrying too much baggage in terms of security concerns. And so, in December 1998, Bucholz McEvoy Architects - then working almost round-the-clock on Fingal County Hall - were commissioned to look at the problem afresh and come up with a solution.

Merritt Bucholz and Karen McEvoy are certainly making their mark. With Fingal completed to great acclaim, they are working on a headquarters for Limerick County Council in Dooradoyle and have just been commissioned by the Dublin City Architect, Jim Barrett, to design a glass canopy for Moore Street in the heart of the city.

It helped the architects that senior civil servants in the Department of the Taoiseach came to accept that they could no longer be so defensive about themselves by having bunkers at its entrance. Even the semantics changed. "It went from security huts to pavilions and, finally, welcoming pavilions," as Angela Rolfe recalled.

As in the case of Fingal County Hall, Bucholz McEvoy took a literal interpretation of the commitment to transparency. "With the previous huts, it was very hard to see in or out," says Bucholz. "So one of the fundamental things we decided to do was to ensure in our design that the visibility of the courtyard was total."

They also separated the Garda/Army component from the "welcoming pavilion" component. Thus, on the left-hand side of the entrance, a new smaller pavilion houses a Garda in front with an armed NCO from the Army in a second bullet-proof glazed cubicle to the rear. Behind them are enclosed toilet facilities and other services.

"Security comes from surveillance, not from big security installations," according to Bucholz. So the larger welcoming pavilion was designed to create an open and transparent expression to the public entering the complex. "When people come in, it isn't about opening a door - the door is opened for you" - and it's glass, too.

The architects saw their pavilion almost as a piece of furniture, offering a contemporary counterpoint to the relatively heavy Edwardian Baroque style of Government Buildings. It had to be lightweight, too, because there was no room for deep foundations. As built, it seems almost to float above the surface like a glass-roofed boat.

The pavilion's zinc-clad roof - a reference to the Edwardian dome - is cantilevered from steel columns, augmented by high-tension steel cables to ensure structural stability. It, too, appears to float above a recessed glass shelf, also structural, which was made in Pisa. "It was a very tricky job, done by skilled craftspeople," says Bucholz.

He acknowledges that without the expert input of RFR, the Paris-based structural engineers responsible for the pyramid at the Louvre and a huge range of other cutting-edge work, "we could not have done this structure". (RFR had previously collaborated with Bucholz McEvoy in designing the glass wall of Fingal County Hall).

One of the major constraints was time, as the two pavilions had to be completed within a month last August while the Government was on holidays. And given that the project involved Paris and London-based engineers (Buro Happold) as well as Italian and Irish contractors (Pierce Healy Developments), this was a tall order indeed.

The two pavilions, with the exception of their GRC (glass-reinforced concrete) panelling, were prefabricated in Turin and then dismantled for shipment to Dublin. "We had to check drawings coming from three different places. There was no question of whether it would work on site. If it didn't, August was shot," Bucholz recalled.

Angela Rolfe agreed that the intricate nature of the pavilions and the tight schedule for their erection "really put it up to Irish contractors to perform" because it meant "a completely different way of doing things". But she is pleased at the way they turned out and the positive reaction from the public for an expenditure of £350,000.

Catering for the public, particularly weekend visitors coming in for tours of Government Buildings, was a paramount concern. Simple bench seating has been provided, with underfloor heating to compensate for the air changes caused by the frequent opening of doors; in summer, the pavilion is cooled by louvre vents, like a car engine.

Services are concealed behind folding maple-veneered doors in a walnut-panelled wall at the rear; it, too, "floats" above a glazed strip below. The floor is mainly beech, with limestone on the main walking surface, while the console unit at the entrance has been ergonomically designed so that personnel can reach everything while seated.

IN THE evening, the welcoming pavilion is lit by uplighters, making it glow in the dark. A pair of tall lighting columns flanking the entrance gates are extraordinarily beautiful, compared to the relatively dull trio in Temple Bar Square, and seem to shimmer even in daytime; they are off-the-peg French designs, originally made for the Stade de France.

Instead of ugly railings, the public entrance is secured by a glass wall and stainless steel handrail - completing a set for what Michael O'Doherty, the OPW's director of architectural services, calls "the CNN view of Ireland". For it is here in Merrion Street, inevitably, that the TV cameras are parked with floodlit Government Buildings as a backdrop.