Thanks for your patience. Assuming that they issue you with notice of redundancy and then require you to work your notice period or place you on garden leave such a clause is likely to be fair and reasonable because you will continue to be employed by them and paid for that time. Therefore, you are still their employee and they can prevent you from earning money elsewhere when they are paying you for that time.
If they were to pay you in lieu of notice, which means terminating your employment immediately but paying you for the notice period, then such a clause would be less likely to be enforced. It does not give you much negotiating power because if they wanted to they can include it and it is not illegal to do so, but it simply means that if you were to breach it, they will find it difficult to enforce it.
You can of course try and get them to agree to its removal, but cannot force them to. You can try negotiating for an increased redundancy as a result of it staying but again, you cannot really force them to offer you anything on top of that they will already pay. So they can leave both the redundancy pay and the clause in place as they stand now. If that was the case you simply have to take your chances and potentially breach it, knowing that if you are no longer employed by them, such a clause would be difficult to enforce anyway.
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