Combine prawns, garlic, sumac, lemon rind from 1 lemon, lemon juice from 1 lemon and 60ml oil in a bowl, season to taste and refrigerate to marinate for 30 minutes.
Thread prawns onto skewers, place on a tray and drizzle with a little extra oil.
Barbecue prawn skewers, turning occasionally, until just cooked through (2-3 minutes).
Combine herbs, spring onion, lemon juice from 1 lemon and remaining oil in a bowl and season to taste. Serve with prawn skewers, warm yoghurt flatbread, smoky aubergine and lemon wedges (flatbread and dip recipes available seperately).