Souvlakia with tzatziki

INGREDIENTS

• 1 kilo boneless pork
• 1 tbsp coriander seeds
• 2 tsp rigani, or dried oregano
• 150ml/5fl oz extra virgin olive oil
• 4 tbsp red wine vinegar
• 1 onion
• 2 bay leaves, roughly torn
• salt and freshly ground black pepper
• ½ cucumber
• 1 tbsp white or red wine vinegar
• 150g/5oz thick Greek-style yoghurt
• 1 clove garlic
• 1 tbsp fresh mint