First up, if you’re using wooden skewers, soak some in cold water for 10 minutes, so they don't burn when you put them on the barbie later. Finely grate the zest of 1 lemon into a large bowl, then squeeze in its juice. Peel the garlic and pound into a rough paste in a pestle and mortar with a pinch of sea salt and black pepper. Tear in half of the parsley leaves, smash together, then add to the bowl with 1 tablespoon of oil. Pull the heads off the prawns and peel off the shells, leaving the tails intact. Run the tip of your knife down their backs and pull out the vein to butterfly them. Toss the prawns in the marinade, then cover and pop in the fridge for 30 minutes. For the salad, squeeze the remaining lemon juice onto a serving platter and add 2 tablespoons of extra virgin olive oil. Finely slice and add as much chilli as you like, then tear over the remaining parsley and mint leaves. Peel and very finely slice the red onion, then toss into the dressing and herbs on the platter. Chop the top and bottom off the watermelon, then sit it on one of the flat sides and slice off the peel. Chop the flesh into 1½cm-wide strips, then into 1cm dice, discarding the seeds, and add to the platter. Chop the cucumber and feta into 1cm chunks and add to the party, then use your fingertips to gently toss it all together. Take a bit of pride in skewering up the prawns, interlacing them with the pancetta as you go – don’t pack it on too tightly. Cook the skewers on the barbecue for about 3 minutes on each side, or until the bacon is crisp and the prawns are pink, then serve on top of the salad.