Prepared by AMSR using the Archive
Structural increase in Prime-Ministerial power
From the 1980s onwards, the British government underwent a quiet but profound transformation: the centre of power shifted decisively towards No.10. This wasn’t a single moment or a dramatic constitutional change. It was a long-term institutional evolution driven by two Prime Ministers — Margaret Thatcher and Tony Blair — who reshaped the machinery of government so that the Prime Minister could direct policy more forcefully and more consistently than before.
Thatcher: Turning No.10 into a command centre
When Thatcher entered office in 1979, No.10 was still largely a coordinating hub. Departments generated policy; Cabinet debated it; the PM steered from the centre. Thatcher changed this model.
- Expansion of the Policy Unit She strengthened the No.10 Policy Unit and staffed it with economists and advisers aligned with her monetarist agenda. This gave her an independent source of analysis and strategy, allowing her to bypass departmental advice when necessary.
- A more assertive Cabinet Office Thatcher used the Cabinet Office to monitor departments and ensure they delivered her reforms. This reduced the autonomy of Secretaries of State and made Cabinet less of a deliberative body and more of a forum for confirming decisions already shaped in No.10.
- Inner circle decision-making Thatcher relied heavily on a small group of trusted advisers — Bernard Ingham, Charles Powell, and her economic team — who operated outside formal Cabinet structures. This informal network became central to policy formation and political management.
- Reduced Cabinet discussion Cabinet meetings became shorter, more controlled, and less central to decision-making. Even during periods of low government popularity, Thatcher maintained personal authority because the machinery of government increasingly revolved around her office.
Structural effect: No.10 became the strategic engine of government, with more analytical capacity, more monitoring power, and more influence over departments than any previous PM had possessed.
Blair: Completing and deepening the centralisation
Blair inherited Thatcher’s more powerful No.10 — and expanded it dramatically. His reforms made the centre not just stronger, but more complex and more professionalised.
- Creation of new central units Blair established the Strategy Unit, the Delivery Unit, and strengthened the Policy Directorate. These bodies gave No.10 the ability to set long-term priorities, monitor departmental performance, and intervene when delivery faltered.
- Communications dominance Blair’s No.10 developed a sophisticated communications operation under Alastair Campbell. Departments were expected to align their messaging with Downing Street, giving the PM unprecedented control over political strategy and public narrative.
- ‘Sofa government’ Blair increasingly relied on informal bilateral meetings rather than full Cabinet. Key decisions — from public service reform to foreign policy — were shaped in small groups rather than through collective Cabinet discussion.
- Target-driven departmental management Through Public Service Agreements and delivery plans, Blair used the centre to direct departmental priorities. Secretaries of State had less autonomy than at any time since the post-war period.
Structural effect: No.10 became a multi-layered executive operation with specialist teams, strategic planning capacity, and direct oversight of departmental delivery.
Why this matters: Institutional, not personal, PM power
By the early 2000s:
- 10 had more staff, more policy units, and more control over departments than ever before.
- Cabinet had become less central to decision-making.
- The PM had structural tools to dominate policy formation, communications, and implementation.
This centralisation represents a structural increase in prime-ministerial power — rooted in institutional change rather than personality, crisis, or political circumstance. Thatcher and Blair did not simply use power effectively; they changed the machinery of government so that future Prime Ministers would inherit a more centralised, more capable, and more dominant No.10.
Prepared by Phyllis Macfarlane with help from CoPilot
2026