The poet William Blake once wrote of seeing "a world in a grain of sand". Mary is doing something similar as she contemplates a small area of earth, less than a metre square in size. She is looking at her family's future. It is a row of about a hundred small plants, an inch high, protected from the sun. Soon they will be planted to become trees. "I sat down with my two older brothers and we decided on this," she says. "It will take 15 to 20 years for it to be a proper forest and we can sell that wood for 600,000 shillings (£540)."

In that small statement, it is possible to glimpse the life Mary was destined to have - a life governed by subsistence farming, where long-term ambition is measured by the growth of trees in a plot. Yet now she has far more expansive hopes after the charity Camfed International intervened to guarantee, at a cost of just £75 per year, that she would have four more years of paid education. Mary is one of more than 1,000 girls Camfed, which the FT is backing for its seasonal appeal, is to support through secondary school in Iringa, Tanzania.