Offering four shows daily six days a week, the Coliseum was a true People's Palace when it opened, in 1904. The original fare was "variety", but that didn't prevent Sarah Bernhardt, WC Fields, Lily Langtry, and Diaghilev's Ballet Russe from gracing its stage. The Second World War turned the Coliseum into an air-raid canteen, after which it became a big-screen cinema; only in 1968, when Sadler's Wells Opera moved in, did it find its present function. Its history since then has been chequered but largely glorious: as the home of opera in English, it is in the true sense our national opera house. Now, after a massive refurbishment, it is about to reopen, in as close an approximation as possible to the guise in which it first appeared 100 years ago.
It's nice to find my hard-hat tour coinciding with the installation of the bar, in the airy glass atrium from which punters will be able to look out over Trafalgar Square and up at the brand-new revolving globe on the theatre's floodlit tower. It's poignant that the foyer's original mosaic floor should be fleetingly re-exposed - health and safety decree that it must be carpeted when the world comes back in. The architects have been sensible (lifts for the disabled, more women's loos) and also clever: they' ve managed to augment the public space by 40 per cent, and the pokey old champagne bar is now an open promenade.
Inside the auditorium, I'm dazzled. Listed status may have prevented any change to the acoustics, but what's now emerging is a thing of beauty. Gone is the keynote tatty blue: the dominant colour, offsetting the warm marble tones, is plum red, with a grand drape over the proscenium where the plastic tympanum used to be. A row of sculpted heads look keenly out below the dress circle; the restored bas-reliefs have a positively Pompeian grace. There's even an inducement to sit up in the gods, since that's where you get the best view of the restored Roman friezes and the now-pristine dome. It all feels a great place to be.
But a £41m refit is only part of what ENO, whose home the Coliseum is, has endured over the last 12 months. It's been bailed out of near-bankruptcy by the Arts Council, seen a strike by its chorus, and suffered 80 redundancies. It's acquired a new chief executive, in what must be one of the messiest boardroom coups in operatic history. The reasons for music director Paul Daniel's subsequent announcement of his departure can only be guessed at. Sean Doran came into the chief-executive hot seat seven months ago, to a near-universal chorus of: "Who he?"
Well, who he? The answer is, a soft-spoken, 43-year-old Ulsterman, whose career to date reveals restlessly creative instincts. He nearly became a professional clarinettist, but opted for a life at that shadowy point where the commercial and subsidised worlds meet. He formed an avant-garde new-music group called Innererklang with Simon Rattle as its president; the need to earn a living drove him to take a job as arts officer at Luton Central Library.
He ran the Derry Festival, then the Queens Festival in Belfast, and was then invited to take charge of the Perth Festival in Australia, which he flashily transformed into the southern hemisphere's Edinburgh. He looks back with nostalgia on his achievements there, which included getting Anthony Gormley to create 50 sculptures in the desert. "That nearly killed me," he recalls. "Convincing everyone that I wasn't mad to put my most expensive production a thousand kilometres from the city centre. Australians really can test your mettle, and I think it was getting through the challenges there that made me ready for a job like this."
A job like this? A poisoned chalice! He smiles. "I'd been told it was a poisoned chalice, but when I came in, I held meetings with people right across the company, 20 at a time, and it was clear there was a hunger and a will for the future. They were bruised, but they were ready to pull together again. Some had been in the company for 12 years and never met one another. There were schisms between departments, let alone with management. A lot has been quite straightforward to put right."
But he admits he was taken aback by the "strong response" to his own appointment: "I only realised just how important this company actually is when I was one or two months in. If it went down, it would be a national loss. The next two years are going to be tough. But at least we know where we're starting from." But where they are steering towards? "We have had to decide what our mission is. We looked at every possible scenario, both artistically and financially, and we concluded that the fixed ensemble ethos was absolutely crucial. Historically it was where the company's strength has lain. It was our main point of difference, and it's where we can deliver artistically that better edge. But once you commit to that fixed ensemble, you have those fixed costs. And when - as happened in the last two years - the box office did drop quite a bit, and every one per cent is a hundred and thirty grand." His voice tails off thoughtfully. "We're going to ensure very strict financial control."
Here, we're in deeper waters, but he insists he's happy with the new management structure. "Though it was put in place before I got here, it's a structure I support. There's an executive director [for financial control] alongside me, though they're not an equal authority. At the end of the day, I am the chief executive." But there is also a chairman: is he ready for that challenge?
"If you're a genuine artistic director, you're isolated and exposed, you' re on the edge, you'll get critically whacked for productions that fail. That scares audiences, and that scares boards, and once the finances start to go, boards go in - I've seen it before - and the only way to press them back out, is for them to feel confidence in you. I'm a firm believer in managing upwards as well as downwards, and you do that on behalf of the company. The chairman is finally in charge, but you've got to manage upwards."
Doran goes to some lengths to praise the commitment of his board, and its cleverness in extracting a £3m sponsorship from Sky. He denies that there was any pressure on him to junk Calixto Bieito's coke-and-fellatio-fuelled Don Giovanni, which he's reviving this season; he defends the production of The Handmaid's Tale, though not to the point of restaging it. He thinks ENO was ambitious in tackling both The Ring and The Trojans in one year, but felt it would be too destabilising to pull one of them at this late stage. Doran promises eight new productions a year, including new productions of revived classics like Carmen and La Traviata, but insists: "As in the past, ENO has got to be adventurous to survive."
"In March," he says, "ENO will unveil a contemporary strand, not in the main house. The Coliseum is our home, our anchor, but we will go out to find new audiences." He has toyed with the idea of getting Steven Spielberg to direct Schoenberg's Moses and Aron.
Meanwhile, he has urgent in-house problems to solve: an angry chorus and the incontrovertible fact that the public does not at present associate English National Opera with great voices. But Sean Doran is a realist, with tenacity and imagination - he finds John Cage's music "Mozartian" - so watch this space.
ENO reopens on 21 February at the Coliseum, St Martin's Lane, London WC2 (020-7632 8300; www.eno.org). ENO is holding a free open day on 29 FebruaryReuse content