World leaders have been warned that Cop26 must “mark the beginning of the end of climate change” amid last-minute talks that could help determine the future of the planet. With the long-awaited environmental summit due to start on Monday, Boris Johnson issued his plea while saying “too many countries are still doing too little”. Speaking en route to Italy to meet other prime ministers and presidents from the G20 group of industrialised nations, Johnson said that without action the modern world could suffer the same fate as the Roman empire…