Mayor Bill de Blasios $130m plan to upgrade New Yorks neglected parks has put the spotlight on a commissioner who likes to go incognito to see how people use his green spaces. Emma Brockes joins himThe best parks and green spaces in US cities: share your favouritesMitchell Silver, the parks commissioner of New York, sometimes goes incognito to one of the citys recreation grounds, just to observe how the people behave there.