This chapter investigates the House of Commons at Westminster in a pivotal period for women’s representation: the first Blair government of 1997–2001. Based on archival, historical and ethnographic data (observations and interviews), the House of Commons is identified as a gendered space, in which women are peripheral members. For example, the overall proportion of turns taken in a sample of debates shows that men break the rules by speaking out of turn more than women. Prime Minister’s Question Time events are ‘scored’ according to the degree of adversarial features that they possess. The findings show that women and men can be equally adversarial in the House of Commons (both women and men were responsible for the most adversarial exchanges), but that women contributed proportionally fewer adversarial turns than their male counterparts. Finally, it is found that women are less likely to manipulate the ‘key’ of a speech event by using humour or irony (particularly the practice of filibustering) than men in this context. Women MPs’ avoidance of rule-breaking (or meticulous adherence to the rules) is explained as one of ways in which women MPs make sure they are beyond reproach in a Community of Practice in which they are interlopers.