London’s Pocket Parks, Holmsdale Tunnel Open Space, Waltham Cross, EN8

Visiting a park just after umpteen heatwaves have lain waste to the land might seem awkward, but to be honest, this park simply changes colour, and that’s all. A long, wide rectangle of grasslands doesn’t seem that interesting, unless you start to wonder why there aren’t any trees – and the reason is just a metre or so below your feet.This parkland sits on top of the M25 motorway, to dampen the noise of motorcars passing through a fairly residential area. Not by much, to