Question regarding redundancy.

[Pottyone]

Where does an employee stand when they have 2 jobs within a company, their 'regular' job and a relief job when a particular area is understaffed? The relief job area is under threat of redundancies (despite being understaffed!). The employee actually spends far more time doing the relief job than his regular job. Will he be at risk of redundancy? The 2 jobs have different pay rates, and he is paid according to which job he does. Will also post this under the Law section as not sure where to post it.