Sam Cassidy is the loyal Personal Assistant and secretary to Malcolm Tucker.
Very little is revealed about Sam's personal life, apart from she may be in a relationship, given a remark about going to an upscale restaurant with someone.
She is implied to have worked for Malcolm Tucker long before the events of Series 1. They have a friendly working relationship, with Tucker holding her in very high regard.
Unlike many other secretaries and admin staff she is not a member of the Civil Service, as she continues to work for Malcolm when he and the party are in opposition.