Preheat oven to 350. Chop Rhubarb and slice strawberries.
Place in mixing bowl.
Add frozen berries, and sugar. Stir to combine.
Add elderflower lemonade. Stir to combine.
Add flour and mix well.
Place pie shell into baking dish.
Pour filling into shell.
Weave bacon into a lattice on top of filling. Fold edges over bacon. Cover with foil. Bake for 1 hour. Uncover and bake for an extra 15-20 minutes until top is crisp. Let cool for 1 hour. Enjoy!