I'd say ruin - in great part from the costs of two World Wars - came before the end of the Empire. Wikipedia notes of WWII - "Britain was left essentially bankrupt, with insolvency only averted in 1946 after the negotiation of a US$3.75 billion loan from the United States". Vs. the Partition and dissolution of the British Raj were in 1947.
Most of the world's gold was in the US by the end of the war.
The flow of gold into the US starting in 1933 is thought to be why the Great Depression was moderating so much there and then: the money supply was inflating.
