Unless you have tasted a particular oil before, there is no way of knowing from the label or the price how good it is, though as a general rule those classified as ‘extra-virgin’ and with a darker green colour will be superior to pale-coloured oils described simply as olive oil. It is not a new dilemma, for the fruit of the olive tree has been eaten since pre-history. The Abyssinians recorded their cultivation of olive trees in 5,000 BC and the culinary importance of the heavy fragrant oil produced from the ripe black fruit has been huge ever since.