Roof leak above window on first floor - Roofing job in Birmingham, West Midlands

Job description

There is a leak above the window on the first floor resulting in dripping and damp. Rain water appears to be entering from the roof and trickling down the cavity. The house has a second floor attic room and so access to the roof from the inside is difficult. There is no sign of a problem in the attic. The links below are photographs of the problem window from the inside and outside.

https://www.dropbox.com/s/zd8csujr0g7imnf/first_floor_above_window.jpg?dl=0
https://www.dropbox.com/s/zvypcfa84e43zfe/first_floor_window_damp.jpg?dl=0
https://www.dropbox.com/s/iz57nxxdylmz8g8/first_floor_window_outside.jpg?dl=0