beginning in 1933, a slightly simplified version of the met's police box design was also used by the city of glasgow police when its old cast-iron police boxes were replaced by an expanded crawley type of integrated police box system. this was done as part of the restructuring of the force brought about by percy sillitoe after he was appointed chief constable at the end of 1931. like the cast-iron boxes before them, the new concrete boxes continued to be painted red until the popularity of doctor who prompted a change to blue in the late 1960s.