An actuated non-return valve (100; 200) comprising: a main valve having a main valve closure (102; 202) and a main valve seat (103; 203) provided inside a body (104; 204); the main valve closure (102; 202) is slidably supported within the body (104; 204) for movement between (i) a closed condition against the main valve seat (103; 203) towards an outlet, low pressure side ("LP") and (ii) an open condition away from the main valve seat (103; 203) towards an inlet, high pressure side ("HP"); the main valve closure (102; 202) biased into the closed condition by a closing spring (153; 253); a by-pass passage (120; 124) extends through the main valve closure (102; 202) with a by-pass valve (126; 226) provided to control flow through the by-pass passage (120; 124); and the by-pass valve (126; 226) includes a by-pass valve closure (132; 232) and a by-pass valve seat (148; 248) located inside a by-pass valve chamber (134; 234); characterised in that: the main valve closure (102; 202) has a central guided spindle (106; 206) which extends away from the main valve seat towards the inlet side of the main valve, the by-pass passage (120; 124) extends within the spindle (106; 206) and the by-pass valve (126; 226) is provided adjacent a free end of the spindle (106; 206) with at least one inlet port of the by-pass passage (120; 124) provided through the spindle (106; 206); the main valve closure (102; 202) is also guided at a side opposite to the spindle (106; 206) on a bearing (112, 212) slidably located on a hollow cylindrical guide (114; 214) supported from the body (104; 204) with the by-pass passage (120; 124) extending from the spindle (106; 206) and inside the cylindrical guide (114; 214) which provides a by-pass outlet from the by-pass passage (120; 124); the by-pass valve seat (148; 248) is annular and the by-pass passage (120; 124) extends through the by-pass valve seat (148; 248) with a control rod that extends from the outlet side of the main valve through the cylindrical guide (114; 214), along the by-pass passage (120; 124) and through the by-pass valve seat (148; 248) to engage the by-pass valve closure (132; 232); the control rod is provided to engage against the by-pass valve closure (132; 232) to apply an opening bias to first open the by-pass valve (126; 226) for a required degree of pressure equalisation across the main valve closure (102; 202) and then move the main valve closure (102; 202) into the open condition; and the opening bias of the control rod is applied to a first side (130; 230) of the by-pass valve closure (132; 232) and a closing bias towards the by-pass valve seat (148; 248) is provided on a second side (146; 246) of the by-pass valve closure (132; 232), opposite to the control rod. a main valve having a main valve closure (102; 202) and a main valve seat (103; 203) provided inside a body (104; 204); the main valve closure (102; 202) is slidably supported within the body (104; 204) for movement between (i) a closed condition against the main valve seat (103; 203) towards an outlet, low pressure side ("LP") and (ii) an open condition away from the main valve seat (103; 203) towards an inlet, high pressure side ("HP"); the main valve closure (102; 202) biased into the closed condition by a closing spring (153; 253); a by-pass passage (120; 124) extends through the main valve closure (102; 202) with a by-pass valve (126; 226) provided to control flow through the by-pass passage (120; 124); and the by-pass valve (126; 226) includes a by-pass valve closure (132; 232) and a by-pass valve seat (148; 248) located inside a by-pass valve chamber (134; 234); the main valve closure (102; 202) has a central guided spindle (106; 206) which extends away from the main valve seat towards the inlet side of the main valve, the by-pass passage (120; 124) extends within the spindle (106; 206) and the by-pass valve (126; 226) is provided adjacent a free end of the spindle (106; 206) with at least one inlet port of the by-pass passage (120; 124) provided through the spindle (106; 206); the main valve closure (102; 202) is also guided at a side opposite to the spindle (106; 206) on a bearing (112, 212) slidably located on a hollow cylindrical guide (114; 214) supported from the body (104; 204) with the by-pass passage (120; 124) extending from the spindle (106; 206) and inside the cylindrical guide (114; 214) which provides a by-pass outlet from the by-pass passage (120; 124); the by-pass valve seat (148; 248) is annular and the by-pass passage (120; 124) extends through the by-pass valve seat (148; 248) with a control rod that extends from the outlet side of the main valve through the cylindrical guide (114; 214), along the by-pass passage (120; 124) and through the by-pass valve seat (148; 248) to engage the by-pass valve closure (132; 232); the control rod is provided to engage against the by-pass valve closure (132; 232) to apply an opening bias to first open the by-pass valve (126; 226) for a required degree of pressure equalisation across the main valve closure (102; 202) and then move the main valve closure (102; 202) into the open condition; and the opening bias of the control rod is applied to a first side (130; 230) of the by-pass valve closure (132; 232) and a closing bias towards the by-pass valve seat (148; 248) is provided on a second side (146; 246) of the by-pass valve closure (132; 232), opposite to the control rod.