Warm the olive oil in a large pot over medium heat then add the onion, carrot and celery. Cook, stirring often, until the onion has softened and translucent, about 5 minutes.
Add the garlic, cumin and curry powder. Cook until fragrant while stirring constantly, about 30 seconds. Pour in the diced tomatoes and cook for a few more minutes, stirring often, in order to enhance their flavour.
Pour in the lentils, stock and the water. Raise heat and bring the mixture to a boil, then partially cover the pot and reduce the heat to maintain a gentle simmer. Cook for 50 minutes, or until the lentils are tender and the liquid has reduced.
Season to taste with both salt and pepper.
Serve while hot with fresh bread.