 When an authority is given discretion, it cannot bind itself as to the way in which this discretion will be exercised either by internal policies or obligations to others.Even though an authority may establish internal guidelines, it should be prepared to make exceptions on the basis of every individual case.Under Lord Diplock's classification, a decision is irrational if it is "so outrageous in its defiance of logic or of accepted moral standards that no sensible person who had applied his mind to the question could have arrived at it."