Bipolar-I Disorder is a common condition that is characterized by periods of mood elevation however periods of chronic and recurring depressive episodes are more common and can be severely disabling. Effective treatments exist, however a significant portion of bipolar depressed patients do not respond to, or have difficulty tolerating many of these interventions. Repetitive Transcranial Magnetic Stimulation (rTMS) is a non-invasive neuromodulatory technique that is effective in major depression and there is evidence for its efficacy in bipolar depression which needs to be assessed in larger randomized controlled trials. This study is a randomised, double-blind, sham-controlled trial over four weeks. The primary objective is to assess improvement in depressive symptoms in acute bipolar-I depressed patients on treatment with intermittent Theta-Burst Stimulation (iTBS) in comparison to sham-rTMS.