Oil production in Saudi Arabia and Iran, Opec’s two biggest members, fell in October as the cartel prepared to implement its 1.2m barrel a day production cut which began on November 1.

The Organisation of the Petroleum Exporting Countries, the cartel that controls 40 per cent of the world’s oil supply, last month announced it would reduce its production to 26.3m barrels-a-day, cutting more than 4 per cent of its output in an attempt to stop the recent 25 per cent slide in international oil prices.