Tony Weir: 'In order to discover what a decision is an authority for, one must first understand the relevant facts, and analyse the decision in the light of those facts, ignoring asides (obiter dicta). The aim is to ascertain the rule (the ratio decidendi) that the judge must have had in mind in order to reach his decision. Then one must decide whether that rule is applicable to the case in hand, which depends on whether its facts are different enough to enable the prior decision to be ‘distinguished’; if so, the judge may disregard the prior decision or, if he thinks it right, extend it to the case in hand'