Preheat oven to 400 degrees Fahrenheit.
Cut the potatoes in half then into wedges. Add the wedges to a large pan of cold water. Bring to a boil, reduce heat and simmer for 10 minutes, or until the wedges have softened but the flesh has not started to disintegrate. Drain well and pat dry on kitchen towel.
Mix the olive oil, garlic, allspice, coriander and paprika in a roasting pan. Add slat and pepper to taste. Add the potatoes to the pan and shake to coat them thoroughly.
Roast for 20-25 minutes, until the wedges are browned, crisp and fully cooked. Turn the wedges occasionally during the roasting time.
Meanwhile make the chilli dip. Heat the oil in a small pan, add the onion and garlic, and cook for 5-10 minutes, until softened.
Pour in diced tomatoes and their juices. Stir in the chilli and vinegar. Cook gently for 10 minutes, until the mixture has reduced and thickened, then taste and adjust seasoning. Stir in chopped fresh coriander.
Pile the wedges on a plate, garnish with extra coriander and serve with chilli dip.