There seems never to be a still second at Kolkata's Sealdah station, barely a moment of pause amid the constant noise and friction of people and cargo in motion. Every day more than 120 trains come and go from the 15 platforms here. It is among the busiest stations in Asia.
This hub is also a place of danger, not least for the hundreds of children who call the station their home. At any given time you will find countless children frantically trying get their hands on a few rupees by foul means or fair, and at any moment those children could fall victim to numerous dangers. There are drugs, sexual abuse, violence from their parents, from other adults or from children just like them.
There is little respite for the children of Sealdah. But for the past decade, an organisation called the Children In Need Institute (CINI) ASHA has provided these vulnerable youngsters with a basic education and somewhere safe to sleep.
Having started with just a small room located on platform 10, the organisation now runs two drop-in centres for boys, aged from five to 14, where youngsters can participate in simple lessons, games and music. As evening falls, they become night shelters. The centres are supported and funded by Child Hope UK, one of the beneficiaries of The Independent's charity appeal.
"The children either live on the station platforms or else on the street in the surrounding area," said Shuvalakshmi Gupta, one of the charity's senior co-ordinators. "Maybe the children are running away from various abuses – sexual or physical. There are many reasons why children might come to Sealdah. We have different activities here: indoor games, arts and crafts. We don't put too much stress on the studies. These children are coming directly from the station. If we try to be too strict, they will not come."
It is a challenge to detail adequately the toxic sensory overload that Sealdah creates. There are unlikely noises, curious smells and distressing sights in abundance. No one knows the place better than Babu Dey, 24, a former railway child who works for CINI ASHA.
He and his family lived in a shack on the edge of the tracks and his father worked making gloves. The money was small and what little his father made was often spent on alcohol. For a child of just three or four, the station was a desperately dangerous place, with drug pushers, thieves and pickpockets.
At night, his sleep would be constantly interrupted by the noise of trains. Then one day, he heard about the newly opened drop-in centre and paid a visit.
"There is no playground in Sealdah but in the centre there was a place to play," he said. "You could be a child." Mr Dey took me on a tour around Sealdah and the surrounding area, pointing out the children who work the platforms as shoe-shine boys or beggars, rubbish collectors or thieves.
Everywhere one looked, there were children: some trying to force open the locked door of a parked carriage to obtain leftover food, one young boy carrying a small plastic bag and wandering the platform in a glue-induced haze, another walking alone along the excrement-encrusted tracks. Children were playing and fighting amid sacks of fresh vegetables.
Sambu, a young boy with a wooden box and a set of brushes, was waiting for customers who could spare a few rupees to have their shoes cleaned. He has been attending the drop-in centre for some months and recognised Mr Dey. He liked going, he said, when he was not sent out to work by his family.
"When I see a new child on the platform, I go and talk to them and try to strike up a rapport," said Mr Dey, who is now studying social work. "I try to understand their feelings. I can empathise with them. I tell them what they can do." The nearby Koley Market is a wholesale vegetable bazaar, where men wearing vests and lunghis carry huge baskets of fresh produce on their heads. Some of the baskets are so large and heavy, they require six men to lift them into the air before one of the individuals places his head beneath the load and somehow makes his way off.
There is an indoor hall for onions alone and at the entrance, sacks of the purple-red vegetables are lifted on to trucks by men using hooks. Here, small, filthy children and old women in rags wait for a lone onion to fall from a sack so they can pounce on it and take it away to sell.
In a place where existences are determined by such narrow margins, even a facility as essentially simple as a drop-in centre can make a huge difference to those who to attend. These centres, where every child is given their own locker and a safe place to sleep, are nothing less than safe havens. At the second centre, there are also frank discussions about legal rights and sex education. The boys are told about condoms, and the risk of HIV. There is vocational training in mobile-phone repair, carpentry, gardening and hotel management.
Sabbir Khan is an 11-year-old boy whose father is too sick to work and who was brought to work at the station as a beggar by his mother. Now he lives at the drop-in centre with his younger brother. They will stay for several months before staff try to find them a place in a hostel.
"Once when I was begging, I saw a child crying so much," said Sabbir, who handed a visitor a gift of two hand-drawn sketches. "But its mother just hit it very hard. We had to take a lot of insults from the people who would very often not give us a penny. There was a lot of verbal abuse."
His friend Tapash is also aged 11. His family is from rural West Bengal, but two years ago he ran away to Kolkata to escape his father, who had repeatedly abused him. "I like coming here to study and to eat," he said. "I also like playing cricket."
The charities in this year's Independent Christmas Appeal
Children around the world cope daily with problems that are difficult for most of us to comprehend. For our Christmas Appeal this year we have chosen three charities which support vulnerable children everywhere.
* Children on the Edge was founded by Anita Roddick 20 years ago to help children institutionalised in Romanian orphanages. It specialises in traumatised children. It still works in eastern Europe, supporting children with disabilities and girls at risk of sex trafficking. But it now works with children in extreme situations in a dozen countries – children orphaned by AIDS in South Africa, post-tsunami trauma in Indonesia, long-term post-conflict disturbance in East Timor, and with Burmese refugee children in Bangladesh and Thailand. www.childrenontheedge.org
* ChildHope works to bring hope and justice, colour and fun into the lives of extremely vulnerable children experiencing different forms of violence in 11 countries in Africa, Asia and South America. www.childhope.org.uk
* Barnardo's works with more than 100,000 of the most disadvantaged children in 415 specialised projects in communities across the UK. It works with children in poverty, homeless runaways, children caring for an ill parent, pupils at risk of being excluded from school, children with disabilities, teenagers leaving care, children who have been sexually abused and those with inappropriate sexual behaviour. It runs parenting programmes. www.barnardos.org.uk