Green campaigner Jeremy Leggett spoke to a Transition Town Tooting (TTT) audience last week.
Mr Leggett spoke about the problem of meeting increasing demands on resources as oil stocks dwindle.
He was joined by Rex Cassidy, facilities director at Springfield Hospital, who looked at the energy challenge of looking after 90 buildings used by 3,000 staff in the Tooting area.
TTT is one of 200 similar nationwide initiative looking at how communities can adapt to the challenges of decreasing oil and climate change.
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