It's in the COS
Go and read sect 32 Redundancy
I'm agree with WESTCOASTCAPT's interpretation
If I get made redundant before guys junior to me you can guarantee that I like many others will take action.
Strangely (for CX) this section of the COS is actually fairly clear in the way that it is written. I'm sure that they'd find a way to try to interpret it differently (ie termination due to a reason other than redundancy). Having said that there are enough law firms around the world who I reckon would take this on a NO WIN No FEE basis. Now I know that I won't get much out of the lawyers from this one, but the company would have to pay, that alone would be worth it.
When you consider the amounts that have to be paid out (6 months salary and full retirement fund)Do you really think the company could be bothered with out of order seniority dismissals after paying out these sums of money and then have the threat of law suits as well.
Second view - think like an accountant briefly - why take such a high salaries charge to the books, ie this would be real cashflow outgoing, when you are managing to convince people to take unpaid leave.