The decline of British power began before the Suez crisis.

This is a historical claim about whether British relative power declined before the 1956 Suez Crisis. True: mainstream historical scholarship holds that Britain's relative economic, financial or imperial decline was under way before 1956, for example relative economic decline from the late 19th century, the wartime debts and US loans of the World Wars, sterling crises (1947, 1949) and Indian independence (1947). Mostly true: historians broadly agree, though some date the decisive turn to Suez itself. Mixed: the scholarship is genuinely divided. Mostly false: most historians treat Suez as the start of the decline, with only minor earlier signs. False: the consensus is that the decline began only with or after Suez.

Set before the research began.

1. E1 SUEZ AND BRITAIN'S DECLINE AS A WORLD POWER* | The Historical Journal | Cambridge Core Cambridge University Press (The Historical Journal) · 15 November 2012

   “Britain's relationship with its informal and formal empire was already changing before 1956, and the turn from the commonwealth to Europe owed little to Suez.”

2. E2 SUEZ AND BRITAIN'S DECLINE AS A WORLD POWER* | The Historical Journal | Cambridge Core Cambridge University Press (The Historical Journal) · 15 November 2012

   “The Suez crisis is widely believed to have contributed significantly to Britain's decline as a world power.”

3. E3 SUEZ AND BRITAIN'S DECLINE AS A WORLD POWER* | The Historical Journal | Cambridge Core Cambridge University Press (The Historical Journal) · 15 November 2012

   “Krozewski believes Suez was important as it ‘revealed how fragile Britain's economy was in the global context without the support of the United States’ (p. 149), but, as noted above (pp. 1101–03), the Treasury was aware of sterling's weakness even before the crisis unfolded.”

4. E4 British Relative Economic Decline in the Aftermath of German Unification Warwick Economics Research Papers (University of Warwick), by Nicholas Crafts · July 2020

   “Evidently, the relative economic decline of the UK which was to continue through much of the 20th century had already begun.”

A peer-reviewed Historical Journal article says Britain's relationship with its formal and informal empire "was already changing before 1956" (E1). It also notes that the Treasury knew sterling was weak before the Suez crisis unfolded (E3). The article notes that Suez is widely believed to have "contributed significantly" to Britain's decline (E2). Nicholas Crafts's working paper on the aftermath of German unification says Britain's relative economic decline "had already begun" by then (E4), which fits the scholarly view that the decline started well before 1956.