• Widespread use of "native" labourers and soldiers. There were remarkably few actual Brits in places like India and Africa proportional to the population.

• Brits died in their droves of tropical diseases and generally not doing well in the climate. Anyone there long term developed something of an immunity.

• It's not a coincidence that the places where White Brits settled - Canada, Australia, the US etc are generally not tropical.

• Often, by adapting around local norms and customs. Resting in the afternoon and working in the evening etc.

Listen to the podcast "Empire" for more, or read "The Anarchy" by one of the podcasters William Dalrymple about the East India Company.