A year ago, Typhoon Haiyan created a series of storm surges that left several thousand people dead and around four million homeless. Lasse Petersen was one of thousands of aid workers who flew to the Philippines in the immediate aftermath of the typhoon.
"When we arrived, we decided to focus our efforts on repairing schools," Petersen says.
"In the poor neighbourhoods where we were working, schools were usually the most solidly constructed buildings. In the early stages, they were used as emergency accommodation for refugees, then as storage facilities for aid consignments and as soup kitchens. Finally they were used as classrooms again as refugees either repaired their own houses or were provided with temporary accommodation.
"Twelve months on, there is a lot still to do. Essential services, such as hospitals, power and water, have been restored, but many public buildings are still waiting to be repaired."
Petersen's first deployment was to Papua New Guinea in 2004, helping people whose village was destroyed by a volcanic eruption. Since then, he has worked in dozens of disaster zones, from earthquakes and floods to hurricanes and tsunamis. He tells me about his experiences after the Japanese tsunami - one of the first disasters to be televised live.
"Like most people, I remember watching the waves coming over the coastline in the TV reports, and seeing cars with people in them being swept away. Within 36 hours, I was with other aid workers in Japan driving towards Sendai. The country had been hit by the fifth-most powerful earthquake ever recorded, but most buildings had survived almost unscathed as a result of some of the strictest building codes in the world.
"Yet as we entered the areas near the coast, where the tsunami had struck, it was the opposite - there were great swathes where almost every building had been completely destroyed. Cars had been picked up and deposited on the roofs of four-storey buildings. Entire towns that had once been home to tens of thousands had been turned to matchsticks. Even when we were standing right there among the wreckage, it was hard to comprehend the sheer physical devastation. It was like being on the set of a movie.
"A year before, I had been working in Haiti. While the thing that stays in my mind about Japan was the damage to buildings, in Haiti the destruction was human as much as it was physical. When our plane landed at Port-au-Prince, there were troops from at least six nations trying to maintain order while thousands of people clamoured for food and water."
You might imagine that years spent in some extremely challenging circumstances would take its toll, but Petersen invariably focuses on what can be achieved.
"I read a children's story once," he says. "A child walks along the beach and sees many starfish washed up and drying out in the sun. The child picks up a starfish and throws it into the ocean. A man sees the child and says: 'What difference will that make? You can't possibly save all these starfish - there are hundreds of thousands washed up; there's no way you can make a difference.' And the child picks one up and says: 'But I can make a difference to this one', and he throws the starfish back in the sea, 'and to this one', as he picks up another, 'and to this one'. To my mind, humanitarian aid is often similar - you just have to make a start, and help one person at a time."
- Independent