'I'm in charge of what goes on in the name of opera at the Royal Opera House." If anyone else were to say this, it might sound like boasting, but Elaine Padmore, the former artistic director of both Wexford Festival Opera and what was then the Dublin Grand Opera Society, is explaining, in her calmly precise way, what it means to be director of opera at Covent Garden.

"I deal specifically with the opera side of things, as opposed to the director of the ballet or the director of the opera house, who's responsible for funding and dealing with the unions and all that sort of thing. I work very closely with producers, designers, artistic teams and, also, the incoming music director, Antonio Pappano. We discuss who's right for the projects we want to do. It's very stimulating - it's great."

Grand opera, you might say. Certainly, for anyone used to opera Irish style, the scale of the thing is mind-boggling. "There are usually something like 22 operas a season, and we've got those planned for the next four to five years. We've got something like 100 operas in the pipeline. Every one of those is cast already, and they've got covers as well. So you have people saying, 'Oh, I need to have three days off on January 8th, 9th and 10th, 2004. Can you arrange that?'"

Happily, the Royal Opera House is also blessed with a director of casting, whose job it is to look after such nitty-gritty details.

It must have been quite a shock for Padmore, after two years of such unadulterated luxury, to find herself rehearsing Handel's mammoth opera Julius Caesar - which she is taking time out from Covent Garden to direct for Opera Ireland - in a church hall in Ballsbridge: from serious state funding to opera seria on a shoestring.

But it's a return to her operatic roots for Padmore, who was a student at Birmingham University in the 1960s, when Anthony Lewis was busy blowing the dust off scores that had been hidden away for years, and helping to stimulate the Handel revival.

"I turned up - aged 18 - I happened to be the best keyboard player and I ended up being repetiteur, so some of the very first operas I ever saw were baroque operas," she says. "I didn't start with The Marriage Of Figaro and the usual things. So I've always had great faith in baroque opera."

With its string of spectacular arias, Julius Caesar is one of the jewels in the baroque crown. It's also one of the most frequently performed of Handel's operas, despite its fearsome length. "If you did this opera uncut, it would be about four-and-a-half hours of music. There is no way any modern audience - except, perhaps, a very specialised one - would want to hear every note, so we're going to do the version that Charles Mackerras made for English National Opera. The one they made the marvellous recording of, with Janet Baker, Charles Tomlinson, Della Jones. Our conductor, Noel Davies, was playing harpsichord at the Coliseum the base of English National Opera then, and has conducted this same edition many times in many different places, so he's closely associated with it."

This is in contrast to Padmore, who has directed just one baroque opera - a somewhat arcane piece written by Gluck to celebrate the birth of a Danish prince - and several key members of the cast, "very talented young singers who are trying themselves out in this style", as she puts it. They include the mezzo Anna Burford in the title role and our own Regina Nathan - "those arias are such a joy, and they fit her like a glove" - as Cleopatra. The countertenor Artur Stefanowicz, who will play the evil Ptolemy, is a considerably more experienced Handelian.

With designs by Bruno Schwengl, the piece will look elegant and simple, promises Padmore. "We have a wonderful lighting designer who has created some very beautiful scenes," she says.

It's instructive to remember that in Handel's day, operas were mostly lit by candlelight. "It was a very simple style of production. Of course they had all sorts of spectacular effects, with gods coming down on clouds and so forth, but basically it was all done with shutters that opened and a whole lot of cloths that came down. These operas have a lot of scene changes. Every other page, practically, there's a stage direction saying, 'A very pleasant prospect', or, 'An anteroom in the palace'."

Simple or not, there could be some unexpected hilarity when scene-changers nodded off for a moment, as the English essayist Joseph Steele noted in a Spectator article following the premiere of Handel's Rinaldo, in 1711. "The Undertakers forgetting to change their Side-Scenes, we were presented with a Prospect of the Ocean in the midst of a delightful Grove, and . . . I must own I was not a little astonished to see a well-dressed young Fellow, in a full-bottom'd Wigg, appear in the midst of the Sea, and without any visible concern taking Snuff."

Mechanical failures and tetchy critics? Sounds a bit like Covent Garden. But that, insists Padmore, was the old institution. She turned down the Royal Opera House job a couple of years back, when the organisation was in the thick of a well-publicised bad patch. "Painfully well publicised," she says.

Instead, she stayed in Denmark for seven years, giving the Royal Danish Opera a badly needed overhaul. "I was specifically asked to give it an international profile; there was a feeling that, as Copenhagen was no longer a sleepy northern town but a European capital with an increasing voice in the EU, they needed to do something about their opera."

She enjoyed the challenge and enjoyed living in Copenhagen, "but it felt like a very long time away from home." So when, towards the end of her contract, another offer came from Covent Garden, with its sparkling new house and its efficient new American executive director, "I thought, yes, this is it."

As a director of one of the biggest houses on the scene, Padmore is one of the people who decides what opera-goers are going to see for the foreseeable future. Does this mean she has to look into an operatic crystal ball and try to predict musical tastes? It could be a dangerous game, given the speed with which Handel opera crashed out of fashion 200 years ago.

"Not really," she says, "because in a sense we are dictating taste. People do go and see the same titles over and over again, but they have to get bored - they have to get fed up with it, eventually. Naturally, Tosca and Traviata and Turandot will always sell out - we know that, and there has to be a certain percentage of those. But you can't . . ." She searches for a metaphor. "It's like living on cake, you know? You have to have some bread as well, and also some spicy food, something exotic.

"We're in touch with the world's top singers and conductors about what they want to do; and about every other year we're planning a new commission. The amount of money you spend on a new opera is colossal - and you don't expect to get the money back, either - but we do want to keep on fuelling our art form. We don't want to say, well, opera has been composed now. We're always looking for people who can push it forward."

Like Mark-Anthony Turnage, whose powerful setting of Seβn O'Casey's The Silver Tassie was given its Irish premiΦre by Opera Ireland last season. But, as Padmore points out, it's an expensive business, and Opera Ireland shouldn't be expected to go on producing miracles on a shoestring. "The situation that I hoped would change when I left Opera Ireland, in 1993, well, it hasn't happened," she says.

"Every time the Gaiety came on the market, there was always talk of, oh, let's buy it, but it hasn't happened, and I'm so sorry, because I think the company deserves it. They've got terrific aspirations, terrific courage. But opera companies need a home. It also saddens me that Dublin is the only European capital that doesn't have its own opera house, especially as there's so much more money around now. All these hotels; I've never seen so many hotels. They've grown up like mushrooms - and there's still no opera house. That's sad. And it's such a pretty theatre, the Gaiety."

She leans over and speaks pointedly into the tape recorder. "It would make a very nice opera house." But that, of course, is a baroque tale of a complexity that would make even Handel's librettists blanch.

Julius Caesar opens at the Gaiety Theatre, Dublin, on Sunday; bookings at 01-4535519 or 01-6771717, or see www.opera-ireland.ie