Mix lemon juice, sugar and jello in hot water to dissolve. Cool slightly.
Beat chilled milk till stiff. Pour lemon mixture oer whipped milk.
Crumble 8-10 vanilla wafers in bottom of a pretty serving bowl. Pour 1/2 mixture in to bowl and stir until mixed. Put the rest of the mixture on top. Crush a few vanilla wafers and sprinkle on top of fluff. Cover and store in fridge for several hours before serving.