Born in 1937 to a Swiss working-class family in Geneva, Gaston said he remembered deciding at six years of age to dedicate his life "to Christ and the poor".

"I never wanted to be a priest," the brother of the Prado congregation told AFP news agency at the Inter-Religious Center of Development (ICOD), an NGO he co-founded in Gohalopata, a village 75 kilometres southwest of Kolkata.

"The church would never have let me live in a slum with the poor, but my life was about sharing with the poorest."

A trained nurse, Gaston arrived in India in 1972 to work with a French priest in a small self-help centre in Pilkhana.

"It was the biggest slum in India at the time, they said in the world!"

Having arrived on a tuk-tuk, he surprised the local residents by entering on foot.

"I didn't want to enter a place where there are so many poor people, on a rickshaw, like a rich person," he said.

"I went to places where there were no doctors, non-governmental organisations, or Christians. That is to say, places that were completely abandoned."

Surrounded by leprosy

At the time of Lapierre's visit, Mother Teresa was receiving medicine from all over the world.

She donated large quantities to the self-help centre, which Gaston was able to use.

He trained nurses and established a dispensary. "I had the medicine, I didn't need anything else," he said. "We quickly had more than 60,000 patients the first year, 100,000 the second. Three years later, we had a small hospital."

As soon as he arrived in India, he decided to adopt the nationality. "It took 20 years, of course," he said.

Gaston was born with the surname Grandjean. In India, he chose the surname "Dayanand", meaning "blessed (ananda) of mercy (daya)".

He worked for a long time with Mother Teresa's brothers caring for people suffering from leprosy in Pilkhana.

'A board to sleep on'

Now white-haired and confined to a wheelchair, Gaston is still trying to help those in need in the northeastern province of West Bengal.

Of the 12 NGOs he founded since moving to India, six are still active, including the ICOD, which has taken in 81 people of all faiths, including orphans and the elderly, as well as those suffering from disabilities and mental health problems.

"I will earn my bread until the last day of my life," he said.