Marine pipelaying vessel for S-lay pipelaying an offshore pipeline and integrating one or more accessories into the pipeline, the vessel comprising: - a hull having a stinger end and two cantilever structures (2, 3) extending at the stinger end of the hull; - pipeline assembly installation including one or more welding stations to weld pipe sections to the end of a launched pipeline; - one or more tensioners (4, 5) downstream of the pipeline assembly installation for supporting the weight of the launched pipeline; - a stinger for guiding the launched pipeline in a curved pipeline trajectory, which stinger is pivotably connected to the stinger end of the hull such that the stinger is pivotable about a horizontal stinger pivot axis, and wherein the stinger extends between the two cantilever structures; - accessory handling J-lay tower at the stinger end of the hull, for supporting an accessory to be connected to the pipeline and for launching in J-lay mode said pipeline with the accessory connected thereto along a J-lay firing line; - stinger support assembly for supporting the stinger in a pipelay position, and for allowing movement of the stinger between the pipelay position and a steep downwardly pivoted retracted position by pivoting the stinger about its stinger pivot axis, wherein the stinger in the retracted position is away from the J-lay firing line; - displaceable hang off clamp for supporting the weight of the launched pipeline when disconnected from the tensioners, which clamp is displaceable while supporting the weight of the launched pipeline between a first position in which the hang off clamp can be clamped on the pipeline downstream of the one or more tensioners during S-lay to allow disconnection of the pipeline from the tensioners and a second position in the J-lay firing line of the accessory handling J-lay tower such that the pipeline supported by the hang off clamp can be aligned with the accessory supported by the accessory handling J-lay tower and can be connected thereto; the J-lay tower allowing the pipeline and connected accessory to be laid in J-lay mode while connecting further pipe sections to the pipeline at least until the accessory has been lowered past below the retracted stinger, characterized in further comprising a displaceable hang off clamp frame in which the hang off clamp is tiltable supported about a horizontal clamp tilt axis, wherein the hang off clamp frame is displaceable substantially horizontal between the first and second position. - a hull having a stinger end and two cantilever structures (2, 3) extending at the stinger end of the hull; - pipeline assembly installation including one or more welding stations to weld pipe sections to the end of a launched pipeline; - one or more tensioners (4, 5) downstream of the pipeline assembly installation for supporting the weight of the launched pipeline; - a stinger for guiding the launched pipeline in a curved pipeline trajectory, which stinger is pivotably connected to the stinger end of the hull such that the stinger is pivotable about a horizontal stinger pivot axis, and wherein the stinger extends between the two cantilever structures; - accessory handling J-lay tower at the stinger end of the hull, for supporting an accessory to be connected to the pipeline and for launching in J-lay mode said pipeline with the accessory connected thereto along a J-lay firing line; - stinger support assembly for supporting the stinger in a pipelay position, and for allowing movement of the stinger between the pipelay position and a steep downwardly pivoted retracted position by pivoting the stinger about its stinger pivot axis, wherein the stinger in the retracted position is away from the J-lay firing line; - displaceable hang off clamp for supporting the weight of the launched pipeline when disconnected from the tensioners, which clamp is displaceable while supporting the weight of the launched pipeline between a first position in which the hang off clamp can be clamped on the pipeline downstream of the one or more tensioners during S-lay to allow disconnection of the pipeline from the tensioners and a second position in the J-lay firing line of the accessory handling J-lay tower such that the pipeline supported by the hang off clamp can be aligned with the accessory supported by the accessory handling J-lay tower and can be connected thereto; the J-lay tower allowing the pipeline and connected accessory to be laid in J-lay mode while connecting further pipe sections to the pipeline at least until the accessory has been lowered past below the retracted stinger, characterized in further comprising a displaceable hang off clamp frame in which the hang off clamp is tiltable supported about a horizontal clamp tilt axis, wherein the hang off clamp frame is displaceable substantially horizontal between the first and second position.