At King's Cross station, a total stranger stopped me on the broad stairway as hundreds of hurrying bodies shuffled by. The question: Are you from Sri Lanka?

Near Russell Square, I played tennis with a Canadian who lived in the same nearby student housing as a woman I'd met from New York.

The Edgware Road station sits a few hundred yards from the Cricketers Club that is home to the St. Marylebone Rotary Club, which hosted me for countless free lunches and dinners during my year as a graduate student in London.

It seemed a lifetime ago and a world away — until July 7, when terrorists paralyzed the Underground with three bombs and blew the top off a red double-decker bus.

How often had I taken the Piccadilly Line from the Finsbury Park station, changing at King's Cross to the Northern Line for a short ride to the Angel and then a walk to City University for classes?

How often had I traversed the city, cautious but not fearful, even though the Irish Republican Army was menacing Northern Ireland, even though notices in all the tube trains warned about reporting unattended packages?

As much as any city on the planet, London encompasses the world in its more than 7 million residents. The sprawling city, with its incredible history, its fundamentally British character, its vast array of ethnic neighborhoods, its international business climate, leaves room for the best — and the worst — of human nature.

It leaves room for misguided, malevolent maniacs to hide within an open society, only to murder innocent bystanders. But it also leaves room for the kind of individual exchange that helps bridge differences across nationalities, cultures and religions.

A Rotary Foundation fellowship sponsored by the Arlington, Texas, Rotary Club made it possible for me to spend the 1979-80 school year in London, studying journalism from a British perspective, confronting personal prejudices and acquiring a broader understanding of the world.

It was an unparalleled education for a Texas naif fresh from college graduation — especially in those days before the Internet, cable TV and cell phones shrank the globe.

I lived on the third floor of an Irish family's row house in a working-class neighborhood. Heat on bone-chilling nights came from a gas meter fed by 5-pence coins. I came to like lamb, steak-and-kidney pie and curry, but it took many months to find a store that sold Fritos, the food I missed most from home.

A fellow journalism student insisted that I spend time with his family in Belfast's largest Roman Catholic enclave, and I marveled at how they functioned with armed British troops patrolling their streets and barbed-wired barracks giving their neighborhood a morbid air.

I took an Easter weekend tour bus trip to Paris with six Britons, six Iranians, four Australians, two Israelis, two Pakistanis, two Greeks, two Italians, two Koreans, two Chinese, a Mexican, a Brazilian, a Panamanian, a Costa Rican, six Colombians and a Nigerian.

An underlying current of class warfare frequently bubbled to the surface, and some labor strike or another often seemed to shut down some type of services in the city.

A Rotarian once asked what advice I could give about mending race relations, given his impression that the United States had succeeded at it while Britain had not.

The recurring question was: "Who shot J.R.?"

But the most enduring lesson I learned was about the power of personal interaction to dispel myths and build good will.

During the spring of 1980, the world appeared to be falling apart. After the disastrous failed rescue attempt of the American hostages in Iran, gunmen seized the Iranian Embassy in London, only to be foiled after five days by a British commando raid.

We forget, sometimes, how terrorists have peddled dread for decades, only to be turned back because civilized people refuse to turn on one another arbitrarily, to see every stranger as a threat.

When terrorists kill, maim and traumatize people, individuals might feel helpless against such brute and indiscriminate force. But they aren't, as long as they understand the strength of unity constructed on an understanding of common humanity.

On a City University condolence Web page started after the London bombings, a graduate identified as Pedro A. Gonzalez Perez said it this way:

"That is precisely one of the best ways to fight against terrorism: the direct contact between people from different countries, cultures, religions or languages. Let's dismantle those fanatics' rule that says that 'different equals evil.' "

Linda P. Campbell is a columnist and editorial writer for the Fort Worth Star-Telegram.