Valve

A valve comprising:

• a first part defining a first aperture and a second part defining a second aperture, the first part being moveable laterally relative to the second part between a closed configuration in which the first and second apertures are not registered to substantially prevent passage of a fluid through the valve and an open configuration in which the first and second apertures are registered to allow passage of fluid, the first and second parts being configured to lock in the closed configuration in response to a pressure differential across the valve and unlock in the closed configuration when the pressure differential across the valve is substantially zero;
• an opening mechanism for moving the first part from the closed configuration to the open configuration;
• a closing mechanism for moving the first part from the open configuration to the closed configuration;
• and
• a trigger for selectively activating the closing mechanism when the first part is in the open configuration;
• wherein the opening mechanism comprises an opening biasing mechanism configured to apply a biasing action when the first part is locked in the closed configuration, with the first and second parts being configured to lock in the closed configuration due to the pressure differential preventing relative lateral movement between the first and second parts whilst the biasing action is applied by the opening biasing mechanism, and wherein the first and second parts are biased to move from the closed configuration to the open configuration automatically once the pressure difference across the valve reduces below a predetermined level.