Many are the poets who have stood in the shade of a great tree and proclaimed its beauty, but what they behold is a mere fraction of the whole. By climbing, we engage all our senses. The textures of different barks and the suppleness of branches that bend under our weight are a stark contrast to the synthetic nature of the world we inhabit at ground level. Pausing in a tree top we can tune in to an alternative soundscape, a world of subtle variation unnoticed in the cacophony of the street; the heavy sigh of a branch buffeted by a lorry's slipstream or a full head of leaves catching the wind off the river. 

Only once, in all the trees I have climbed across the city, have I found someone sitting in the top of one. The man I encountered was small, grey and smiling. He was at least sixty, dressed in suit trousers with his shirt untucked and a jacket and tie hanging on the branch below him. Once we had gotten over our mutual surprise - and I'd taken a subordinate perch - we began talking. This man was no great libertarian, no anarchist or antichrist. He was simply a lawyer on a lunch break having his sandwich in an ash tree. This decision, to eat at altitude above the packed square of the park, was not a radical one. To me this man was following the most natural inclination in the world - a desire for breathing space and a different point of view. 

Trees deliver us from the banal, and reaching the top of one is like coming up for air and breaking the bubble of our timetabled lives. Their physical complexity, together with the courage needed to climb them, liberates thought and offers a wealth of natural knowledge. The treeline acts as a defence against the darker parts of urban living and the canopy is an inviolate place, a still room for reflection amid the constant rush of city life.