Cook the pasta in boiling salted water with 2 sprigs of the mint for the time given on the packet. 3 minutes before the end of the cooking time, add the peas. Once the pasta and peas are cooked, drain in a colander and shake under cold running water until cool. Discard the mint sprigs.
Transfer to a large bowl and add the feta cheese, rocket, remaining mint, the lemon zest and half the juice, salt and pepper and a good glug of olive oil. Either roughly chop or smash the olives in a pestle and mortar and add to the pasta. Toss well and add more lemon juice, seasoning or olive oil, if preferred.
Pack in suitable containers for taking on a picnic or serve warm as part of a main course or starter with a barbecue.