This was never going to be easy watching, or listening, as people who were pretty certain that the hour of their death had come in two of the world’s most iconic buildings, made phone calls to their loved ones. All these years after 9/11, I still find it very hard to imagine what that must’ve been like.

For those on the planes who, like Ted Olsen’s wife, Barbara, knew that the hijacked planes – one of which she was on – were being flown into buildings in the most audacious and destructive act of terrorism that we’ve ever seen, she knew she was going to die, and horrifically.

One young man on one of the planes called his father and told him what was happening. He knew too that he was going to die and he told his dad, “Don’t worry dad. If it happens, it’ll be fast.”

The entire programme was of course filled with the final phone calls of many, many people, some captured forever on answering machine tapes, others similarly captured in the minds of those who took the calls.

For those people who received last messages on their answer-phone tapes, it’s a double edged sword; they know that if they’d been at home, they’d have spoken to their loved one in person during the last moments of their life. However, as they didn’t, at least their voices will never fade from memory.

As one of last night’s interviewees, Anne Mulderry, was in that situation. When her son Stephen called her from one of the Towers, she was at a yoga class. Anne returned home and heard Stephen’s message during which he told her that a plane had hit the Tower and that he would call when he was safe. He told her he loved her. Anne then received a call from her husband begging her not to turn on the TV. Anne said, “It was an easy promise to keep. I went out into the back yard, and I sat on a five dollar plastic chair under a tree, preparing myself for what I would need to face.”

When her daughter called her to tell her that Stephen was most likely dead, Anne issued a “howl”, the like of which she didn’t realise she was capable of.

Another dreadful set of calls was made by Jim Gartenburg to his wife, his friend and to various media outlets. His call to one of the major news channels was played live on air and in it, Jim bravely asked that the families of people trapped in the Towers shouldn’t panic because, he said, “the danger has not increased.”

We heard too from the family of firefighter Orio Palmer who, in one of many acts of outstanding heroism that day, fought his way up floor after floor of one of the Towers to rescue people. Just minutes after his last radio transmission, the Tower collapsed and Orio was gone.

However, arguably the most spine chilling call that we heard last night was made by Kevin Cosgrove. He was talking to an emergency services operator, imploring them to hurry as he and the people with him couldn’t breathe. At the end of the call, a tremendous rumbling sound could be heard and at that point, the call ended, as did Kevin’s life as the Tower collapsed. That call, in part, was used in the trial of one of the suspected Al Qaeda members. The horror of it is truly unimaginable.

And there was the equally sad story of Melissa Harrington-Hughes who called her father and husband when she became trapped during a business meeting in one of the Towers. Her father Bob explained his helplessness as his daughter, panicked and tearful, called him, and there was nothing he could do to help her. “She was in trouble and she called her father for help and I was 130 miles away.”

Bob planted a tree outside his house soon after Melissa was born, and it’s now a huge and verdant reminder of his lost baby. As with many things when someone we love dies, the symbolism of it for Bob is that it’s a living thing, possibly imbued with something of Melissa, and he treasures it.

Anne Mulderry added what I believe was the summation of the point of showing this film when she said, “The world doesn’t stop for every tragic loss of life. I kind of wish the world could.

“The world gets too busy and I understand you can’t. You would be in constant grieving.

“It’s too easy for me to fall into a place where life is only about endurance and that’s a very poor way to live life.

“Don’t lose sight of the big things. Embrace life and its joys.”

I know that there are many people who are tired of hearing about 9/11 and avoid the many programmes about it, but needless to say, these are people who didn’t lose anyone that day. But to those people, I think this programme is an apt reminder that, no matter what the circumstances, no matter what the cause of the tragedy was, when you’re in the midst of grieving, the world carries on around you and it feels like an alien place to be.

So while some of us may feel we’re sufferers of 9/11 fatigue, a reminder that when it all comes down to the wire, and when death is minutes away, possessions mean nothing, ambition means nothing, everyday worries mean nothing; all that matters is who you’ve loved and who loves you.

It surely can never be bad thing to be so forcibly reminded of that by, as in this programme, hearing for ourselves the last desperate calls of those who knew their lives were about to end.