Marine reel lay method pipeline installation vessel for laying on the seabed a pipeline and one or more accessories (3a, 3b) which are to be connected to the pipeline, forming a launched pipeline having a weight, wherein the vessel comprises: • one or more pipeline storage reels for storage of pipeline to be laid; • a pipeline launch tower mounted to the vessel, which pipeline launch tower is adapted to launch the pipeline in a firing line along said tower; • a pipeline guide (10; 100) which is supported at an elevated position by the pipeline launch tower, which pipeline guide is adapted to guide the pipeline from the storage reel over the pipeline guide into the firing line, • one or more tensioners (12, 13), each tensioner comprising a tensioner frame (12b, 13b) supported by the pipeline launch tower and multiple tracks (12a, 12b) supported by said tensioner frame, said tracks being adapted to engage the pipeline and to support at least part of the weight of the launched pipeline in the firing line, • a hang off device supported in the lower part of the firing line, adapted to clamp and support the weight of the launched pipeline in the firing line; • an abandonment and recovery (A&R) system comprising at least one A&R winch and A&R cable, and an A&R sheave arrangement with one or more sheaves (17a,b) provided at an upper position in the firing line, said one or more sheaves being supported by the pipeline launch tower, adapted to raise, lower and support the weight of the launched pipeline in the firing line; • an accessory handling device adapted to position the accessory in an accessory position in the firing line between the hang off device and the A&R sheave arrangement; characterized in that the one or more tensioner frames (12b, 13b) are displaceable supported by a tensioner rail which is mounted to the pipeline launch tower, extending parallel to the firing line, allowing the one or more tensioners to be displaceable in the firing line, along the pipeline launch tower, at least between an upper accessory handling position wherein the one or more tensioners have moved above the accessory position and a lower pipelaying position wherein the one or more tensioners at least partially overlap the accessory position, and in that a tensioner displacement drive is provided to support and displace the one or more tensioners along the pipeline launch tower. • one or more pipeline storage reels for storage of pipeline to be laid; • a pipeline launch tower mounted to the vessel, which pipeline launch tower is adapted to launch the pipeline in a firing line along said tower; • a pipeline guide (10; 100) which is supported at an elevated position by the pipeline launch tower, which pipeline guide is adapted to guide the pipeline from the storage reel over the pipeline guide into the firing line, • one or more tensioners (12, 13), each tensioner comprising a tensioner frame (12b, 13b) supported by the pipeline launch tower and multiple tracks (12a, 12b) supported by said tensioner frame, said tracks being adapted to engage the pipeline and to support at least part of the weight of the launched pipeline in the firing line, • a hang off device supported in the lower part of the firing line, adapted to clamp and support the weight of the launched pipeline in the firing line; • an abandonment and recovery (A&R) system comprising at least one A&R winch and A&R cable, and an A&R sheave arrangement with one or more sheaves (17a,b) provided at an upper position in the firing line, said one or more sheaves being supported by the pipeline launch tower, adapted to raise, lower and support the weight of the launched pipeline in the firing line; • an accessory handling device adapted to position the accessory in an accessory position in the firing line between the hang off device and the A&R sheave arrangement;