The future of the architectural profession faces continued uncertainty in the twenty-first century. Changes in the next 20 years are likely to leave the profession with a smaller and less defined centre, finely balanced between competing art and commercial roles, and those architects who are able to maintain a generalist building design/management approach. Based on existing trends, and personal experience in the profession, this thesis finds the influence of traditional practices will become limited to small scale and niche projects - should the title of architect survive continued government scrutiny. With or without title protection, the findings here suggest that the architectural field will continue to be characterised by more rather than less rapidly changing satellite functions, and roles in all areas competing for economic, Cultural, and - increasingly important in creative sectors and urban growth - knowledge capital. Relative to the increasingly contested, compromised, and privatised nature of architecture practice, this thesis focuses on debates and practice frameworks outside the mainstream of building -centred architecture. It investigates selected accounts by architects, of their practice trajectory since the late twentieth century, to reveal and analyse different approaches to architectural agency, focusing on influencing better quality shared environments. The thesis aim is to reveal a better understanding of architects' evolving professional identities and practice roles. It sets out a unique framework by which architecture and urban space can be conjointly characterised and evaluated as reciprocal outcomes of more critical and transformative practice. It contributes new knowledge about architects' personal strategies and practice frameworks that advocate greater open-ness and use-value for shared civic space, in contrast to more objectified and controlled exchange-value outcomes. The methodology combines sociological and architectural theories. It adapts concepts from key treatise including Bourdieu's agent-field analysis and Unger's philosophy of transformative vocation, interpreted with Till's proposals for critical spatial practice in architecture, and Perez-Gomez's concepts of architectural praxis as conscious applications of architects' knowledge and ethics to practice. The thesis analyses and locates architects career accounts as new practice frameworks within the background of shifting traditional architectural norms and the broad field of contemporary architecture practice. In-depth interviews with selected architects collect narratives about architects' knowledge and skill, examining them for lessons about better shared civic activity and how creative knowledge can include critical and transformative motives while satisfying more instrumental issues of survival, and also gaining esteem and influence. The analysis focuses on professional-identity claims and diverse practice approaches rather than individual projects in isolation, to examine thresholds of architectural knowledge, key moments of action, personal values, and identity. The broader context of how the professional field of architecture and its governing bodies, including the Royal Institute of British Architects (RIBA), debate practice futures is also set out and discussed. The thesis argues that different critical practice trajectories share a combination of personal intention and motivations that are conceptualised as a form of professional habitus and compared with established professional norms. It questions existing understandings of participation and place, and argues for architects to (re)balance their instrumental and transformative design knowledge in response to changing professional and social contexts. Conclusions support (re)framing architects creative knowledge toward a more socially-driven critical design praxis, to effectively engage in an increasingly globalised and interconnected urban society.