Place all the marinade ingredients into a food processor and blend until smooth. Pour into a large bowl and stir in the lamb cubes. Mix well and leave to marinate in the fridge for as long as possible, preferably overnight. Bring back to room temperature an hour before cooking.
Preheat the grill to medium. Thread the lamb cubes onto the skewers leaving a space between each piece and place under the grill. Cook for around 5-6 minutes, turning halfway through cooking, until tender. Alternatively, cook in an oven preheated to 200C/400F/Gas 6 for eight minutes. Baste with the melted butter and cook for another minute or two for slightly pink meat, or longer if you want the lamb well done.
Divide the lamb pieces into five equal portions and place each portion in the centre of a warmed tortilla. Top with a handful of the sliced vegetables and a spoonful of chutney. Roll up and serve.