It's not just any old fruit tree either i'll have you know. It's the beginnings of The Best EVER Braeburn Apple Espalier.
The Art of Espalier has been practised since the Middle Ages to grow trees inside castles and up on walls to save space. I love the idea. Easy to pick the fruit, space efficient and decorative all in one. I also heard that the controlled pruning actually helps the fruit mature faster. So all round.. why wouldnt you do it? A matter of having time i guess.