This chapter analyses the role of non-party parliamentarians, including ‘Crossbenchers’ and bishops in the House of Lords, in the Westminster legislative process and parliament’s impact on policy. Westminster is highly unusual in having around 200 members in the Lords who take no party whip, and who have the potential to influence decision-making as ‘pivotal voters’. Many of these members are recognized experts, with considerable persuasive power. This chapter summarizes their organization, the (very limited) existing literature on their contribution, and the roles that they played on the 12 case study bills. In several cases, non-party parliamentarians were vocal, and successful, in securing legislative change. More generally, this group has subtle forms of influence over the whole dynamic of debate in the Lords, and in parliament’s power of ‘anticipated reactions’. Under the coalition government, particularly on the Welfare Reform Bill, such parliamentarians were more assertive, but with limited policy success.