Two of the big six accountancy firms came to the altar this week, full of hopes and promises for a bright and profitable union.

The marriage brings Price Waterhouse and Coopers & Lybrand together as the largest accountancy firm in the world, to be collectively known as PricewaterhouseCoopers (PwC).

Price Waterhouse brings a larger staff and higher fee income to the partnership. In Ireland, the merged firm will employ 1,133 staff, comprising 632 from Price Waterhouse and 501 from Coopers with the potential to earn fee income of more than £63 million this year.

Price Waterhouse senior partner, Mr Donal O'Connor, has taken over at the enlarged Irish operation while Coopers & Lybrand managing partner, Mr Bill Cunningham, assumes the role of deputy.

As he settled into his new role this week, Mr O'Connor, dismissed any suggestion that Price Waterhouse was in any sense taking over Coopers. "It is a merger of equals. We are trying to focus on the fact that the merger will give us much greater strength and depth and we will benefit from greater efficiencies," he says.

Mergers have become a way of life in the accountancy sector. All of the large firms have grown out of them and a month after the Price Waterhouse/ Coopers & Lybrand union was announced, KPMG and Ernst and Young unveiled proposals to combine their businesses. These have since foundered.

Globally the merger will create a giant firm moving ahead of its rivals with combined revenue of $13 billion (£9.4 billion) employing 135,000 staff and 8,500 partners. It will also mean that half the world's top 100 companies will be audited by one firm if the current business mix is maintained.

News of the merger came as a surprise to staff at both firms when it was revealed last September. Mr O'Connor says he was told about three days before the formal announcement. "While I couldn't say it was a huge shock, it certainly wasn't something that was on our agenda."

At that stage, Mr O'Connor says he would have known Mr Cunningham "slightly". Over the past 10 months, the two men have had to forge a working relationship and would now claim to know a lot more about each other's management style.

"We have gotten to know each other very well. I have huge regard and admiration for Bill and have enjoyed working with him from day one," Mr O'Connor says. "If we didn't work well together it would be very hard to expect others to."

The greatest concern for staff when such a merger is announced is the impact on their careers. Mr O'Connor explains this was one of his first tasks when the news broke, to assure staff the merger would not lead to job losses.

"Whenever there is a merger there are concerns, but this is happening at a time when the economy is very strong and both firms are doing well. There are no plans to reduce the number of partners or staff. We will not be letting people go and will be recruiting an additional 100 people. I believe this is a most positive message as far as the staff are concerned."

A leadership team, consisting of eight senior partners four from each firm will effectively act as a steering group for the new enterprise. A second layer, which has yet to be finalised, will then be put in place.

The team will run the various services areas and in the final shake-up while no partners will lose their jobs, Mr O'Connor states that some won't find themselves doing exactly the same job. "But that would happen with or without a merger in response to looking at the services we provide to clients," he adds.

For some partners and other senior staff, the merger is not necessarily good news. The distribution of top jobs is being watched closely and has already been the source of disgruntlement. Some will undoubtedly feel that the swelling ranks will cut the chance of promotion and may seek out other employment.

Mr O'Connor accepts the firm will probably lose some people. "I would like to think people will give it a chance. It would be unrealistic though to say some people won't leave. But I would be very disappointed to see a lot of people leave. It's going to be a great place to work and be part of."

In the long term, he says, it is difficult to predict what the structure will be and the size of its workforce.

"At the moment we are very short of people. What happens down the road will depend on the market place. That will dictate what happens. At the moment the signals on the economy are very strong and we will be keeping our operations under review. In the short to medium term the outlook is very positive for staff."

Between them the two firms have some of the biggest Irish public companies as clients and it remains to be seen if it can retain all of them, particularly in the financial services sector where the greatest potential conflict of interest arises.

Coopers is auditor to AIB while Price Waterhouse undertakes the same function for Bank of Ireland. Just how well the two main banking rivals will enjoy sharing the same auditor will be closely watched by its rivals over the coming months.

Mr O'Connor states that all clients have been made aware of potential conflicts of interest and have been assured that detailed procedures will be adhered to where the firm acts for rival corporations. "We have had extensive consultation with clients, explained the impact of the merger to them and addressed any fundamental concerns. I hope they will see that our procedures work."

The leadership team will also tackle the cultural differences between the two organisations.

Mr O'Connor insists much of this is perception. "We will have to focus on what we can agree on. It will be a matter of being flexible and not a matter of doing things in a certain way. We would probably agree on 90 per cent of things from a cultural point of view anyway."

The overall strategy for the firm will be planned by a global leadership team, but the Irish division will retain autonomy over most of the running of its operations. "About 90 per cent of the decisions will be taken locally," he says.

The match was made at global level on the basis that the two firms complement each other. Coopers is for example very strong in Europe, while Price Waterhouse has a substantial presence in South America and Asia. Coopers is also extremely strong in the telecommunications sector while Price Waterhouse is a leader in the technology field.

Their combined strengths are expected to fuel rapid growth, with a global target of 20 per cent growth this year. It will be looking for strong growth in Ireland but Mr O'Connor says it has not tied down a figure yet.

The two firms will continue to operate from their respective offices, with headquarters in Dublin at Wilton Terrace and George's Quay. They will eventually live under the same roof, hopefully within the next three years, Mr O'Connor says.