If you continue to exert influence as a shadow director after your resignation, you can still be liable.
Also, resigning as a director does not allow you to walk away from problems that occurred while you were a director - you retain responsibility for things you did (and sometimes things that you did not do), or that happened, on your 'watch'. For example, if the company subsequently becomes insolvent, the official receiver (or administrator, etc) will look into the conduct of the directors over the previous three years.
