This case has an unusual spin on the EU Collective Redundancies Directive (No.98/59). The CJEU Directive does not expressly define the concept of 'redundancy', the term has to be regarded as a concept of EU law which cannot be defined by reference to the laws of the Member States. That includes cases such as this, where the employee requested that he be made redundant following a 25% unilateral cut to his pay.
http://www.bailii.org/eu/cases/EUECJ/2015/C42214.html