SPD - Task assigned by System Account - Content Organiser

Hi

I have a document Library with approval.

I used the ootb sharepoint approval workflow and the email that gets sent out has the user name of the person who started the workflow. i.e. Task assigned by Tim Watkins on ..

I then created my own List workflow in SPD using the 'Start Approval Process' , when the user starts the wf the email has 'Task assigned bySystem Account on ..' . The workflow's email definition is [%Workflow Context:Initiator%].

How can I get the user name here? Should I simply use document created by ?

Thanks