She describes it as the day she became a New Yorker; almost in the same breath inhaling the toxic fall-out of the collapsing Twin Towers and the new-found humanity of the city.

Yet for Louisa Griffith-Jones, being a couple of blocks down from the World Trade Center when the towers collapsed, has left an indelible physical, mental and emotional imprint on her life.

It is the one constant that has shaped her thoughts, outlook and well-being in the decade since September 11, 2001.

Louisa, 44, arrived in New York in early July 2001 and was part of the Anglia Television production team that was working on the Animal Precinct programme with the American Society for the Prevention of Cruelty to Animals (ASPCA).

As the production co-ordinator, she lived in a 35th floor studio apartment in West Street, Manhattan, just a couple of blocks up from the World Trade Center.

She recalled how she had stayed in on the evening of September 10 as her friend, Nikki, had arrived for a visit from the UK.

'The next morning, I was woken up by an enormous sound,' said Louisa. 'Nikki came out of the kitchen and said 'what was that?'.

'I could see construction workers at the end of the island looking up and there were people running around and screaming. I switched the television on and there were reports of an explosion at the World Trade Center with initial reports that a small plane had hit the tower.

'We got in the elevators to go down to have a look but while I was in the elevator the second plane went right over the top of us.

The building shook and there was a really loud noise. Some people had gone up onto the rooftop to see what was going on and they were now running down and screaming. It was just hysteria.

'When the elevator doors opened we went down on to West Street and the first thing I saw was two burning towers... There were people running out of the towers just after the planes had hit and then there were people falling.

'Initially it was bodies falling and then it was people. We stood there watching – it was horrific. There was a collective gasp when the bodies started to fall and people were crying 'oh, no; oh no'.'

Roads were snarled up with traffic in the blocks around the Twin Towers and she recalls the anguish of a woman who was due to meet her family but was late and did not know whether they were trapped inside.

As she continued to head towards the towers, she said: 'All the time people were jumping. I remember seeing a really tall guy in a suit falling and he was fighting it all the way with his arms swirling round.

'I could not watch as they hit the ground but you felt as though you had to watch them falling, out of some kind of respect, being with them for the last seconds of their lives.

'That is the thing that really upsets me, to wake up one morning and then just watch people dying and knowing there was nothing you could do was just heart-breaking.'

As they neared the police line, they realised that Anglia producer Paul Berriff was ahead of them, already filming the tragedy as it unfolded and the last moments of the World Trade Center before the Twin Towers fell.

Louisa said: 'Nikki was an architect and as she looked up, she said: 'that building is going to come down'. We said, 'it won't, it can't', and then there was an almighty rumble – it was so loud – and it started to come down on the south side and towards us.

'We started running but I was wearing my flip flops and kept stumbling. Every time we looked behind us there was this enormous mountainous cloud just tumbling down the road and getting closer and closer to us. The noise was intense and then the cloud hit us; we could not see, breathe or speak, all we had was a sense of feeling.'

With Nikki, she found a truck and clambered into the cab as two other women climbed in the other side. They found wipes and tried to clean the grime off them as one of the women – a construction worker – began vomiting into her helmet as other terrified survivors dashed past the truck, desperate for refuge from the falling debris.

As the density of the debris cleared a little, Louisa and Nikki headed back to their apartment building, arriving in the lobby to find it crowded with people who had fled from nearby hotels, many of them still in their pyjamas and in obvious shock.

It was then that Louisa noticed fine shards sticking into her skin – minute fibreglass spikes from the collapsing buildings.

'As I tried to wash it off, the second tower came down and there was a terrible rumble again. The doors of our building had been locked but there were people caught outside, hammering on them to be let in. It really was terrifying.'

Management staff refused to open the doors, fearing that the dust cloud would engulf the interior of the Battery Park apartment where they stayed until late afternoon, only venturing out to buy coffee and sandwiches from a local caf�.

Back in the UK, Anglia staff members were trying to arrange their evacuation from Manhattan to the home of a US colleague. As they walked across Brooklyn Bridge to a rendezvous point, they turned to see Tower 7 crumple and fall.

In the days that followed, as New York, America and the world tried to come to terms with the attacks, Louisa and her colleagues were allowed to return to the apartment to recover documents, passports and credit cards and also locate the cat she was fostering at the time. After a lengthy search of the studio apartment, she eventually found it hiding in the sofa.

And by the Sunday, after the attacks of Tuesday, September 11, the crew was back filming – recording a special documentary on the animals being rescued by the ASPCA from the carnage of 9/11 and reunited with their owners.

They eventually left New York on October 23 but Louisa went back in April 2002 and continued to work on the Animal Precinct show until January 2005 and then worked as a freelance in New York until September 2007 before returning to Norfolk to live back in Norwich.

For Louisa, now the communications manager for Norfolk and Waveney Mental Health Trust, there has been a legacy, a long-term emotional, physical and mental impact of being caught up in the attacks and she remains concerned about how it has affected her health.

'In 2006 I had a bad bout of bronchitis and signed up to the WTC health registry to get checked over,' she said. 'I was diagnosed with asthma, I have damaged sinuses and a damaged oesophagus and been told that I have mild Post Traumatic Stress Disorder. Seeing those people jumping does something strange to your brain.'

She has undergone periods of therapy and has regular health check-ups but still reacts badly to aircraft unexpectedly flying over and has nightmares.

Louisa has donated the purple flip flops she was wearing on that day to the 9/11 Memorial Museum.

'They were what every woman seemed to be wearing in New York that summer,' she added. 'Mine had a piece of the tower embedded in them. I thought they should go to the museum so in 2009 I went back over and donated them. It turns out that shoes are most-donated item to the museum, it was all about people running. Flip flops also seemed symbolic of that year; it was summer and September 11 was such a clear blue sky day.'

She also left a 10,000-word audio account of her experiences.

For the 10th anniversary, Louisa will take part in a 5k fun run for the Big C cancer charity in Norfolk on the morning before pausing at the time of the memorial ceremony later in the day. She chose Big C because she is concerned that cancers could claim more 9/11 victims.

'It is now 10 years since the attacks and that is when a lot of people think the cancers will start to kick in. The death toll from 9/11 is going to rise; people have breathed in the carcinogenic material, the fibreglass and all the concrete so they are ticking time-bombs.

'I will respect the day and the time,' said Louisa. 'I know where I was when the first bell sounds and when the second rings. I became a New Yorker on that day, I breathed in the air of that day and it has changed my body, it has changed how I view things.

'I have possibly been a bit more reckless with my life since then, than I might have been but when you live through something like that you know how lucky you are to be alive.

'It has been hard, it has been very hard. I have lost friends, people who did not understand or do not like the way you have changed, but I have made friends too. But life moves on and you have to build a new life.'