I think he is in a relatively strong position compared to others, because the way his employment contract has been handled is bizarre.
If some jobs are declared redundant (cut-backs not the complete closure of the place), the employer has to select employees from a pool of potentially redundant employees. The selection of the pool has to be shown to be fair. If the employer declares those of doing his original job to be part of the pool, then picks him for redundancy, he could turn around and say 'but 90% of the time I do this other job - and are you not making that redundant - I'll have you for unfair dismissal (or words to that effect!)If it's the other way around, he could say 'you employed me to do this - I helped you out - I'll go back to the original job thanks, or I'm having you for unfair dismissal'.