To answer the question, you basically have to prevent the First World War, and keep the geopolitical status quo. Britain needs to maintain the ability to stabilise the Gold Standard at the international level.
More than preventing the First World War, to keep the Classical Gold Standard you would have to deflect demands for nominal wages higher than the classical gold standard allowed by Europe’s working classes – who supported
fiat paper currency long before World War One.
I have long imagined that but for climatic deterioration in Australia and Africa after 1895, the Classical Gold Standard could have collapsed in
the late 1890s or the 1900s without any major war. Gold outflows from resource-poor Northern Hemisphere nations like Japan and the United Kingdom were problematic before that climatic deterioration (“
Federation Drought”) and with the advances in
lithophile metallurgy in the 1920s and 1930s they would likely have even without a war stretched class conflict in Europe and East Asia to breaking point.
Maybe if the old monarchies had not been removed, they would in some parts of Europe and East Asia have in the 1920s and 1930s been able to eliminate democracy and return to more traditionalist absolute monarchies, who would have been strongly supportive of keeping the classical gold standard in its entirety. The trouble is that with the above-mentioned improvements in metallurgical technology, gold outflows to natural-resource-rich arid zone countries would under “retraditionalising” regimes in Europe have put further downward pressure on nominal wages – and of course nominal wages are notoriously “sticky” downwards even should falling money supplies increase
real wages.
Nevertheless, I
do see potential benefits if a “retraditionalising” 1920s and 1930s Europe and Japan could allow for theoretically necessary reductions in prices and wages to match their resource poverty. Most especially, they would be
less specialised in skill- and education-intensive goods and services, dependence upon which has contributed to lowest-low fertility and long-term declines in global power for these nations. At the same time, the resource-rich nations of the lower latitudes might under a gold standard gain higher
real prices for their resources due to the absence of wage floors in natural-resource-impoverished high latitude nations. This might mean better development and living standards in Africa and tropical South America, and I am not sure that the resource-surfeited desert nations of Australia, Southern Africa and the GCC would gain more power – in actual history these nations
undersell their resource wealth and gain enhanced profits from doing so.