I think a staff member is going to bring a claim for unfair dismissal what shall I do?

If the employee has already been dismissed, you must ensure that they have been given a right to appeal that decision. The employee will then need to commence ACAS Early Conciliation to raise their claim before issuing employment tribunal proceedings. The ACAS Early Conciliation will give you advanced warning of the claim and enables you to decide whether to offer a resolution, such as a settlement payment.