I am currently seeing out my notice period at the investment bank where I work. What steps can I take to prepare for the role at my new employer ahead of starting and what limitations does my current employment status entail?

The answer to this question depends on the job you do, how senior you are, whether you are a director of your employer and what your contract of employment says. It also depends on what you mean by 'steps'. There is a big difference between brushing up your foreign language skills at one end of the spectrum and, at the other end, copying details of your employer's unique formulae and algorithms onto a memory stick with a view to taking them with you when you leave.