An apparatus for connecting and disconnecting tubulars of a tubing string suspended in a well, comprising: a top end connector for connection to a tubular axially projecting from said at least one connector, and at least one main high pressure conduit communicating with said at least one connector for providing circulation through a tubular connected to said at least one connector; a connecting shell bounding a connecting chamber, said connecting shell having an upper passage and a lower passage for receiving tubulars, seals (21, 22) for sealing off said passages (19, 20) against tubulars extending through said passages, a gate for separating an upper portion of said connecting chamber from a lower portion of said connecting chamber, and a back-up high pressure conduit communicating with said lower portion of said connecting chamber; a first engagement structure for engaging a tubular projecting from above into said upper portion of said connecting chamber; a second engagement structure for engaging a tubular projecting from below into said lower portion of said connecting chamber; and at least one implement for controlling an opening (61; 261) for receiving a tubular of a drill string, tubing string or casing string, for reversibly closing off the opening (61; 261), sealing off the opening (61; 261) against the tubular and/or engaging the tubular said at least one implement bounding said upper passage or said lower passage or forming said gate; wherein at least said top end connector is movable up and down relative to said connecting shell between a position above said connecting shell and a position in said connecting shell; characterized in that the at least one implement comprises: a carrier sleeve (62, 63; 262) surrounding the opening (61; 261), at least one jaw (64-66; 264) carried by said carrier sleeve (62, 63; 262) and mounted to said carrier sleeve (62, 63; 262) so as to be movable into and out of said opening (61; 261); and an operating sleeve (67; 267) rotatably suspended relative to the carrier sleeve (62, 63; 262) so as to be rotatable relative to the carrier sleeve (62, 63; 262) about a central axis (60; 260) of the opening (61; 261); wherein the at least one jaw (64-66; 264) is coupled to the operating sleeve (67; 267) for urging the at least one jaw (64-66; 264) into said opening (61; 261) in response to rotation of the operating sleeve (67; 267) relative to the carrier sleeve (62, 63; 262). a top end connector for connection to a tubular axially projecting from said at least one connector, and at least one main high pressure conduit communicating with said at least one connector for providing circulation through a tubular connected to said at least one connector; a connecting shell bounding a connecting chamber, said connecting shell having an upper passage and a lower passage for receiving tubulars, seals (21, 22) for sealing off said passages (19, 20) against tubulars extending through said passages, a gate for separating an upper portion of said connecting chamber from a lower portion of said connecting chamber, and a back-up high pressure conduit communicating with said lower portion of said connecting chamber; a first engagement structure for engaging a tubular projecting from above into said upper portion of said connecting chamber; a second engagement structure for engaging a tubular projecting from below into said lower portion of said connecting chamber; and at least one implement for controlling an opening (61; 261) for receiving a tubular of a drill string, tubing string or casing string, for reversibly closing off the opening (61; 261), sealing off the opening (61; 261) against the tubular and/or engaging the tubular said at least one implement bounding said upper passage or said lower passage or forming said gate; wherein at least said top end connector is movable up and down relative to said connecting shell between a position above said connecting shell and a position in said connecting shell; characterized in that the at least one implement comprises: a carrier sleeve (62, 63; 262) surrounding the opening (61; 261), at least one jaw (64-66; 264) carried by said carrier sleeve (62, 63; 262) and mounted to said carrier sleeve (62, 63; 262) so as to be movable into and out of said opening (61; 261); and an operating sleeve (67; 267) rotatably suspended relative to the carrier sleeve (62, 63; 262) so as to be rotatable relative to the carrier sleeve (62, 63; 262) about a central axis (60; 260) of the opening (61; 261); a carrier sleeve (62, 63; 262) surrounding the opening (61; 261), at least one jaw (64-66; 264) carried by said carrier sleeve (62, 63; 262) and mounted to said carrier sleeve (62, 63; 262) so as to be movable into and out of said opening (61; 261); and an operating sleeve (67; 267) rotatably suspended relative to the carrier sleeve (62, 63; 262) so as to be rotatable relative to the carrier sleeve (62, 63; 262) about a central axis (60; 260) of the opening (61; 261); wherein the at least one jaw (64-66; 264) is coupled to the operating sleeve (67; 267) for urging the at least one jaw (64-66; 264) into said opening (61; 261) in response to rotation of the operating sleeve (67; 267) relative to the carrier sleeve (62, 63; 262).