WEST HAVEN, Conn. — Yale Provost Andrew Hamilton, a well-tailored Englishman known for his eloquence, does not often lose his composure. But he did just that when he first toured the science complex here that has now become Yale’s West Campus, replete with hundreds of thousands of square feet of state-of-the-art laboratories.

“President Levin teases me because he says I started to salivate as we walked around these wonderful labs,” Hamilton said with a laugh. “My jaw dropped and saliva dripped out.”

To Hamilton, a chemist by trade, that tour was like Christmas morning. To the University, it was a key milestone in a frenetic, behind-the-scenes scramble to bid for what, for decades, had been the sprawling campus for the pharmaceutical company Bayer HealthCare. But with Bayer set to move out of state and to put the site on the auction block, Yale had to decide whether to throw its hat in the ring — and quickly.

In interviews this month, senior University administrators and other officials involved in the acquisition of the Bayer campus described in unprecedented detail the roller-coaster process that netted Yale its largest land expansion in its history. For an institution obsessed with deliberate, long-term planning, it was an utterly unfamiliar whirlwind — but one that could change the face of Yale forever.

When Hamilton walked into the first laboratory on that fateful tour, his mind was quickly made up. Just weeks later, University President Richard Levin stood here at a hastily convened press conference to announce that Yale had acquired the Bayer complex — and increased the size of the University’s campus by a third in the process.

Levin did not mince words in describing the magnitude of the moment.

“It’s a once-in-a-lifetime opportunity,” he said.

The story of the Bayer acquisition has sad beginnings.

On Nov. 9, 2006, the struggling pharmaceutical giant announced it would close its 137-acre complex — which straddles the town of Orange and the city of West Haven — jeopardizing the jobs of over 1,000 local employees. The banner headline in The New Haven Register was unforgiving: “Bayer Bails,” it screamed.

While the company had been bleeding staffers for months, the announcement still came as a severe blow to the city of West Haven. State officials had even assembled an assistance package worth $60 million in an attempt to keep Bayer from leaving.

It was to no avail.

While a small handful of Bayer employees remain at the complex to this day — ghettoized to a small office building in the western corner of the property while they await relocation — the nearly-vacant campus is a far cry from what it once was. In its heyday, the pharmaceutical company had been the second-largest employer and largest taxpayer in West Haven.

“The past couple years, they were somewhat downsizing,” said State Representative Stephen Dargan, a Democrat whose district includes the Bayer complex. “But we never thought that they would leave West Haven.”

To this day, the town of Orange still has not gotten over the hurt of Bayer’s abandonment. Adorning the town’s welcome sign near highway I-95 lingers the engraving “Bayer Healthcare.”

But in the Bayer bummer came an opportunity for Yale. The company’s announcement was a prominent topic of discussion at a meeting of Yale’s officers in November 2006.

“A comment was made, ‘Well, maybe it’s something we should look at,’ ” recalled Linda Lorimer, Yale’s vice president and secretary.

The consensus at that time, according to senior administrators who were in attendance at that first meeting, was that Yale should keep an eye on the site and what prospects developed for its reuse. To make things easier, Bruce Alexander, the vice president for New Haven and State Affairs and Campus Development, had been appointed to a commission assembled by Connecticut Gov. M. Jodi Rell to recruit suitors for the site.

Alexander, Lorimer and Hamilton were diplomatic in describing the University’s view on the Bayer site: If a pharmaceutical company were to express interest in the property, Yale would have deferred to the commercial interest, they all stressed.

“We all agreed at that point was that if there was going to be a pharmaceutical company that was going to come in and replace the 3,000 jobs that Bayer used to have there,” Alexander said, “that would be the best solution for the economy of the region.”

But to Yale, the appeal of the complex was undeniable.

“Our immediate reaction was, ‘This would be an amazing opportunity for us if we could get it,’ ” Levin said.

But Yale was not alone in its interest in the site. Like vultures, dozens of prospective buyers eyed the carcass that was once the Bayer complex.

All but one had the same plan: Put up big-box retail and demolish the laboratories, or convert them to corporate offices. The bids were underwhelming, those familiar with the negotiations said. And at that point, Yale did not appear a potential suitor for the site, according to Dargan, who sat on the governor’s commission with Alexander.

“A couple things became obvious from the meetings of this commission,” Alexander explained. “One was that there was no pharmaceutical company [interested] … and that the developers that were interested in the parcel were not valuing and would likely not use the laboratory space.”

By last spring, some six months after Bayer first announced its plans to shutter the West Haven site, Alexander went to his fellow officers with a call to action. “I said, ‘This space may well go to waste if we don’t take an interest in this,’ ” he recalled.

So he and Hamilton surveyed the site, as did Yale’s other officers, and the University made its move. Bayer was receptive; after four decades in West Haven, executives cringed at the thought of their state-of-the-art laboratories meeting the wrecking ball in preparation for another Wal-Mart.

“Bayer themselves felt that having this campus kept intact and having this research space used for the benefit of mankind was a very positive thing for them,” Alexander said.

But that was only part of the issue. At the end of the day, Yale still had to win the auction. The University went to lengths to ensure word of its interest in the complex did not leak out to the media, for fear that it would raise the bidding for the property, Levin acknowledged.

It was an unusual process for a university so endeared to long-term planning and careful study by committees. Yale officials have worked behind the scenes for a decade in planning the construction of two new residential colleges on Science Hill, for instance. Such is the case at Yale’s peer institutions, too: Harvard University’s expansion into the Allston neighborhood of Boston has been mapped out to 50 years, and Columbia University’s controversial expansion in Manhattanville will be rolled out over more than two decades.

Yet the acquisition of the West Campus, as Hamilton put it, came together “almost in a matter of days.”

After three rounds of bidding, Yale did what it failed to do in this year’s rendition of The Game: It won. For $109 million, and not a penny more.

Its deep pockets only slightly lighter, Yale walked away from the bargain a winner, paying a fraction of what it would cost to construct comparable buildings in New Haven. The deal was especially attractive to Orange and West Haven, after Yale affirmed a commitment to continue using the property for scientific research.

Because Yale is a not-for-profit institution, the towns will lose tax revenue under the site’s new ownership, as the state’s Payment In Lieu of Taxes (PILOT) program and Yale’s voluntary contributions will not fully cover the loss.

But it could have been worse, officials in the towns say. The many businesses competing for the campus — which did not value its laboratory space but merely wanted the massive tract to redevelop commercially — could not even pony up half as much money as Yale, despite the fact that the newest laboratory on the property, for example, cost $57 million to build, said James Zeoli, first selectman for the town of Orange.

But for Yale, a $109 million price tag was an afterthought, a footnote, a veritable rounding error. The University paid in cash.

“Yale got a bargain that they couldn’t turn down,” Zeoli said. “Yale couldn’t afford to build all that office and science space for that kind of money — they couldn’t have come close.”

Indeed, Yale officials estimate the cost of erecting comparable state-of-the-art laboratories in New Haven at $650 and $700 per square foot. By contrast, the average cost per square foot of the Bayer facilities was about $73.

“To me, it was instinctive,” said Levin, the Frederick William Beinecke Professor of Economics. “Five hundred fifty thousand square feet of science space, I know what that means. Just from an economics point of view, it was irresistible.”

Hamilton, a scientist at heart, described his first reaction as one of grief.

“There was tragedy in how so many fine scientists had lost their jobs as a result of the closing,” Hamilton said.

“But coupled with sadness was excitement,” he added. “Yale had a role to play potentially in the future in using the site for what it was intended to be used for — which was to do cutting-edge science.”

Today, the laboratories at the West Campus still sit empty. But in a matter of months, they will begin to come back to life. West Haven might have lost Bayer, but in these parts, officials are heaving a collective sigh of relief.

“I had said, ‘Wow, this is a big loss for West Haven,’ ” Dargan said.

Now, his tune has changed.

“I hate to use the analogy of baseball,” the lawmaker added, “but it was a home run for the city of West Haven.”

For part two, a tour of the Bayer campus, see Wednesday’s News.