A method is for performing work in a well and on a vessel. A wellbore assembly such as a tool string is suspended on a first flexible elongate member from the vessel. The wellbore assembly is used to perform work in the well. The wellbore assembly such as a tool string is suspended on a second flexible elongate member from the vessel. The wellbore assembly on the first flexible elongate member is removed from the well, and after the removal, the wellbore assembly on the second flexible elongate member is inserted into the well. The inserted wellbore assembly in the well can then be used to perform further work. The wellbore assemblies may be deployed and retrieved on independently operable wirelines. A related vessel and apparatus is also described.