A standstill seal configured to form a seal with a rotatable shaft so as to prevent leakage of a process fluid past the standstill seal when the shaft is not rotating, the standstill seal comprising: a flexible band surrounding the shaft, the flexible band comprising a relatively thicker central region from which relatively thinner side regions extend longitudinally in the direction of sealing of the central region with the shaft , or with an intermediate structure that is sealed to the shaft, when seen in an axial cross-sectional view, the central region being substantially rectangular in longitudinal cross section; a housing configured to house the flexible band; a pair of cover plates underlying the side regions of the flexible band and configured to prevent the side regions from being deflected past the cover plates, a gap being provided between the cover plates through which the central region of the flexible band can be extended; a control fluid inlet configured to provide fluid communication between a source of pressurized control fluid and a rear surface of the flexible band; and a controller; the standstill seal being configured, when the controller applies the pressurized control fluid to the control fluid inlet , to press the rear surface of the flexible band toward the gap , thereby extending the central region of the flexible band through the gap, such that it makes contact and forms a seal with the shaft , or with the intermediate structure that is sealed to the shaft, whereby flexibility of the flexible band is provided by the side regions ; the standstill seal being configured, when the controller ceases to apply the pressurized control fluid to the control fluid inlet , to withdraw the central region of the flexible band away from the shaft or intermediate structure. a flexible band surrounding the shaft, the flexible band comprising a relatively thicker central region from which relatively thinner side regions extend longitudinally in the direction of sealing of the central region with the shaft , or with an intermediate structure that is sealed to the shaft, when seen in an axial cross-sectional view, the central region being substantially rectangular in longitudinal cross section; a housing configured to house the flexible band; a pair of cover plates underlying the side regions of the flexible band and configured to prevent the side regions from being deflected past the cover plates, a gap being provided between the cover plates through which the central region of the flexible band can be extended; a control fluid inlet configured to provide fluid communication between a source of pressurized control fluid and a rear surface of the flexible band; and a controller; the standstill seal being configured, when the controller applies the pressurized control fluid to the control fluid inlet , to press the rear surface of the flexible band toward the gap , thereby extending the central region of the flexible band through the gap, such that it makes contact and forms a seal with the shaft , or with the intermediate structure that is sealed to the shaft, whereby flexibility of the flexible band is provided by the side regions ; the standstill seal being configured, when the controller ceases to apply the pressurized control fluid to the control fluid inlet , to withdraw the central region of the flexible band away from the shaft or intermediate structure. <EOS>