Gorse
If the stabbings and billboards are getting you down, take a trip to Blackheath for some natural prozac. Tom writes: 
"My native Blackheath is covered in Gorse bushes. They get very dry in high summer, and regularly go up in flames when a cigarette butt is cast into their midst from a passing car. In spring and early summer however, they’re dotted with pretty yellow flowers which are have a coconuty smell and a believed to relieve depression, a condition rife among Londoners.
"Sprinkle the washed flowers over a biryani for a comforting curry, or mix with seasonal leaves as a salad."