1) Place the prawns in a shallow dish and add the lemon zest and juice, garlic, salt, pepper and olive oil. Toss the prawns to coat evenly with the dressing.
2) Arrange the rocket in piles of two or three leaves, working with six piles at a time. Pile up three slices of prosciutto in three stacks and cut each stack in half.
3) To assemble the prawns, place one prawn on each pile of rocket leaves then wrap the leaves up with the prawn using a piece of the prosciutto. Assemble six pieces at a time, like an assembly line. Nest a grape tomato into the curve of the prosciutto-wrapped prawn and secure into place with a cocktail stick.
Arrange the prawn starters on a platter and serve. Remember to put out a small empty bowl near the prawn platter to collect the discarded prawn tails and cocktail sticks.