Barbecued Prawns

Ingredients

• 400g tin peeled tomatoes
• 75g brown sugar
• 60ml cider vinegar
• 2 tbsp Worcestershire sauce
• 1 tbsp Dijon mustard
• 3 garlic cloves finely chopped
• 2 tsp ground coriander
• 2 tsp ground cumin
• ½ tsp each ground cinnamon
• ½ tsp ground fennel
• ½ tsp paprika
• 80g butter, coarsely chopped
• 2kg green Skull Island prawns
• Olive oil