Bet she didn't know either ! As a part of crowd control the police may apply to have streets in an area subject to control. The streets may be closed to pedestrians or made one way or whatever is necessary and the police may also direct individuals or pedestrians generally as to movements. It's an offence not to comply with the direction . (This is why streets around Twickenham become mysteriously barred to pedestrians on international match days ) I expect that the contractors have been delegated the actual directing, but the area in which this was was subject to such a control order for the duration of the event.