Finding 29-year-old's McCluskie's head marks the completion of a gruesome jigsaw puzzle for police.
Her torso was pulled from the canal in March just days after she was reported missing. An arm was found less than two weeks later, then her legs, then her other arm.
Her brother, builder Tony McCluskie, 35, was arrested during a police raid on the home he shared with Gemma in Bethnal Green, east London, and has been charged with her murder.
The actress played Kerry Skinner in the popular TV soap in 2001.