see http://www.met.police.uk/asu/ see http://www.google.co.uk/search?q=london+police+helicopter&hl=en&rls=com.microsoft:en-gb:IE-SearchBox&rlz=1I7ADFA_en&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=8Gl7TveVLOOx0QWB6MijAw&ved=0CEAQsAQ&biw=1024&bih=514 The Police Helicopter unit is based at Lippitt's Hill,about 1/4 mile from where I was standing.