Mediterranean Salad

2 handfuls of salad greens – include bitter greens such as rocket or watercress
1 egg, hardboiled and sliced
1 handful of mixed red onion and cucumber, sliced
½ palm-sized portion of tuna, tinned in brine or spring water
4 black olives (optional)
1 tbsp of extra virgin olive oil
1 tbsp of lemon juice or vinegar (e.g. apple cider or red wine)