al446,
Actually, first in last out is NOT illegal. However, the employer using this principal for the purposes of redundancy may NOT mix and match any other arrangements - in other words the system of first in last out MUST be applied accross the board.
It is also worth noting that no employer may fill a position vacated by redundancy for a period 6 months. If there is a need to fill such a position it must first be offered to the person who vacated it.