Zest and juice 2 of the limes into a big
salad bowl. Top and tail the remaining
2 limes to sit flat on a chopping board.
Use a small serrated fruit knife to cut
away the peel and pith in downward
strokes. Cut the segments from the pith
and roughly chop. Add to the salad bowl
with the apples, fennel, cucumber, celery,
spring onions and olive oil. Cover and
chill until ready to serve.