Between at least some of the radiation steps, the articles are shuffled (i.e. their order in the stack is changed) so that the radiation dose is sufficiently uniform, e.g. the maximum dose at any point is not more than 1.5 times, preferably not more than 1.4 times, particularly not more than 1.3 times, especially not more than 1.2 times, more especially not more than 1.1 times the minimum dose at