His point then was, and presumably still is, that we can deal with the moderate warmth of a British summer by simple changes in behaviour and building design, and forgo the expense and complexity of air conditioning.
We can design buildings to restrict solar gain, use thermal mass to limit heating cycles, and allow air to circulate through vents, windows and convection stacks (which is, accidentally, the format of many traditional brick houses). However, it is rarely done in big cities, partly because of the noise and particulate pollution from the streets. There are examples that use some of these techniques, such as Portcullis House in Westminster for MP accommodation and Bloomberg’s European HQ in the City of London, but they are as famous for their extremely high cost as much as their green credentials.
As vehicles become electric, city air will be cleaner and quieter, and the demand for natural ventilation is sure to blossom, and not just to reduce carbon emissions.
The COVID virus, like many other pathogens, is recognised now as a predominantly airborne threat, which becomes rapidly diluted in the open air and degraded by sunlight.
Outside air is COVID safe, while conditioned air needs to be carefully managed, and people are suspicious about its quality. Occupants are already demanding the safe option, and developers will need to look carefully at carbon reduction with some very basic physics.