In 2005 the UK Atomic Energy Authority revealed that its audit for the previous year had failed to account for 30 kg of plutonium, enough to make a number of powerful nuclear bombs. Fortunately, they had not had thirty 1 kg lumps of plutonium stolen by terrorists. The error lay in a 0.1% discrepancy between the amount of plutonium received in spent fuel rods and in the reprocessed material they had delivered. In the edible oil processing industry it would be very difficult to balance the inputs and outputs of a refinery to the stringent standards required for nuclear reprocessing even though 0.1% of a refinery’s output could be worth a large amount of money. The presentation will look at the difficulties of monitoring oil flow and losses in a refinery and how it might be possible to do better. Whenever you take a measurement you have to consider how the measurement was done and the likely error. We shall look at some surprising examples that show how easy it is misinterpret what you think you are measuring. The presentation will be a repeat of the one prepared for the February meeting in Australia.