Abstract: A control mechanism for a retractable reeled tape comprising tape wound on a rotatably mounted spindle so as to be retractably deployable therefrom to selected lengths, said control mechanism comprising: a pawl and tooth arrangement bearing on the spindle such as, when engaged, to permit rotation of the spindle in a direction whereby tape is wound onto the spindle, but to obstruct rotation of the spindle in a direction whereby tape is unwound therefrom; and a clutch mechanism operable to disengage the pawl such that, with the pawl so disengaged, the spindle is free to rotate in either direction. A barrier tape dispenser incorporating such a control mechanism, a tape barrier system comprising multiple such dispensers, and a temporary barrier incorporating such dispensers on suitable uprights, are also described.