A valve assembly for wellbore, downhole or intervention operations, such as for subsea wellbore operations includes a rotatable valve member having a passage formed therein. The valve assembly is reconfigurable between a first configuration in which the passage is aligned or alignable with a first conduit, and a second configuration in which the passage is misaligned or misalignable with the first conduit, so as to cut or sever and/or clamp apparatus present in the valve member passage prior to reconfiguration. The assembly is configured to apply a maximum cutting force at a particular phase or stage of the reconfiguration.