Trim the fennel bulbs, reserving the fronds, and discard the tough outer layers. Using a very
sharp knife, slice the fennel lengthways as thinly as possible and put in a bowl of cold water with
the lemon juice.
Just before serving, drain the fennel well and pat dry with paper towels. Toss in a bowl with
the olive oil and red wine vinegar. Finely chop the fronds, add them to the fennel with the olives
and season to taste.