By Peter Gould BBC News Online in New York

At Ground Zero, Mary Williamson walks along the lines of tributes to those who died on 11 September.

Her husband John was one of 343 New York firefighters killed trying to save the occupants of the World Trade Center.

St Paul's Chapel, close to the spot where the Twin Towers once stood, has become an unofficial shrine to all the victims.

One year on, the messages of support attached to the church railings have been faded by the sun and smeared by rain.

I think that we hold our freedom, and our gifts, and our way of life so much more closely to our hearts now

Mary Williamson

But the words are indelible, an expression of a nation's shock at the enormity of its loss.

Mary is clearly moved by the sentiments. Some of the most touching tributes are drawings from schoolchildren.

"I am delighted to see everything is still here," she said. "I like the fact that September 11 is still fresh in people's minds. This is hallowed space, it is a quiet place for contemplation."

Desperate wait for news

Mary tried to come down here that night, twelve months ago, but found the area sealed off.

She had been unable to find out anything about her husband, a battalion chief in Lower Manhattan.

Her worst fears were confirmed when his body was recovered from the wreckage of the North Tower.

Mary Williamson: Charities were overwhelmed

"Many, many families have not found their loved ones," she says. "I was fortunate because John was found a week after he was killed, and so it has helped me to move on.

"But we still have many families who are overwhelmed with grief."

Mary has listened to tapes of radio conversations between the firefighters, as they converged on the World Trade Center.

Among them, she heard the familiar voice of her husband, John.

"I hope those tapes are released some day so other people can hear them," she said.

"The firefighters sounded so calm and professional, doing their jobs."

Today Mary focuses on the needs of her teenage children, Jessica and Marc.

She also works on projects aimed at ensuring that the millions of dollars of charitable donations made after 11 September reach the families in need.

Overwhelming generosity

Initially, she says, the charities faced difficulties because of the magnitude of the tragedy, and the scale of the response.

"I think the charities were overwhelmed by the generosity of the public," she said.

"There was a lot of chaos at first, but that was only to be expected, and things have settled down."

Many families have not found their loved ones. I was fortunate because John was found a week after he was killed

Mary Williamson

There have been problems about defining who should receive assistance. Not all families fit in to the traditional legal union of marriage.

And the relatives of some people listed as missing are still clinging to the hope that they might turn up alive.

"There are still many families out there who are waiting to hear something from their loved one, and until that issue is resolved, it is difficult for them to move forward," said Mary.

She has been working with her local Congressman on legislation that will require charities to ensure donations by the public go to the intended recipients, and do not simply disappear into a large pot.

Pain of loss

One year after 11 September, bereaved families are still dealing with the pain of their loss.

Many have spoken about the strength they have gained from the messages of support received from all over the world.

Mrs Williamson inspects a shirt left near the site

Mary is still receiving letters from complete strangers who want her to know her family is in their thoughts.

"I have had letters and packages from children in schools all over Europe," she said.

"It is amazing how children see these events. They are so honest and straight forward with their questions. They write letters saying I hope your missing husband will be found and come home soon.

"The past year has been an amazing odyssey. September 11 was an event that everyone who has lived through will carry with them for the rest of their lives.

"I think that we hold our freedom, and our gifts, and our way of life so much more closely to our hearts now. We realise how valuable they are."

Click here to watch residents of New York give their views about September 11