Combine all of the ingredients for the burgers in a large bowl and, using your hands, mix until the ingredients are evenly incorporated.

Divide the mixture into 4 evenly sized balls and using your hands form each ball into a patty. Make a small indentation with your thumb in the center of the burger to ensure it cooks evenly.

Preheat the barbecue or a grill pan to medium high heat and once up to temperature, cook the burgers for 4 minutes per side until cooked through (but don't overcook as they dry out).

Cut the pitas in half and open them into pita pockets. Fill each pita with a lamb burger, slice of tomato, big scoop of tzatziki, red onion, crumbled feta, some chopped kalamata olive and arugula.