Place tuna in a bowl and mash with a fork, then add celery, black pepper and salt and mix thoroughly.
Add scallions and mix thoroughly once more.
Add mayonnaise and mix thoroughly again, then set aside.
Place spinach and arugula in a bowl and add balsamic vinegar and toss, then set aside.
Place two slices of bread on top of each other and remove the crusts, and repeat until all crusts have been removed from all eight slices of bread.
Place four crustless slices of bread onto a bread board, then add a layer of the spinach and arugula on top.
Cover spinach and arugula with seasoned tuna, then top with peppadew.
Place the remaining slices of bread on top to make a sandwich and then press sandwiches together, just a little.
With a sharp bread knife cut the sandwiches in half, then cut those halves into quarters.
Place sandwiches on a serving plate and serve immediately.