Using wooden skewers? Soak them in cold water for 10 mins. Toast 1 tsp coriander seeds in a dry frying pan for 1 min till they smell fragrant. Tip into a pestle and mortar, and crush (or use the end of a rolling pin in a bowl).
Peel and crush or finely chop the garlic. Mix with the coriander seeds and ½ tsp of the cinnamon. Finely grate the zest from the lemon and set aside. Squeeze the juice from half the lemon and add to the spices and garlic.
Slice the venison steaks into strips. Add to the spices with 1 tbsp olive oil. Turn to coat. Set aside. Slice the cucumber down its length and scoop out the seeds. Coarsely grate half the cucumber. Squeeze out as much liquid as you can with your hands, then stir the flesh into the yogurt.
Rinse and trim the radishes, keeping the leaves for later. Finely slice the radishes and the leaves.
Rinse the mint. Pat dry. Strip the leaves from their stems and tear them. Stir them into the yogurt with the radishes, radish leaves and lemon zest. Season with salt and pepper.
Heat the grill to high. Line the grill pan with foil. Thread the venison strips onto the skewers. Season with a little salt and pepper.
Grill the venison skewers for 8-10 mins till they are a little charred and cooked through.
While the venison cooks, rinse the salad leaves. Dry in a salad spinner or pat dry with kitchen paper. Pop in a bowl. Dress with the lemon juice from the remaining lemon half, 1 tbsp olive oil and some seasoning. Serve the salad with the venison and the twistziki.