If you are representing a client (or yourself) in the employment tribunal – or any other court or tribunal, come to that – your job is to put your case to the best of your ability. The judge’s job is to decide on the outcome: that’s what they’re paid for.
Judges don’t always remember this. Sometimes you will come under considerable pressure to concede part of your case, or to agree that a view the judge expresses on the law at the beginning of the hearing is correct. Judges are supposed to be experts on the law, and lots are: but some aren’t, and even the best are wrong sometimes. So if the judge tries to get you to agree that he or she is right about some legal proposition that you’re worried about because it seems to make it harder for you to win, don’t assume you have to back down. You don’t: you are entitled to argue in favour of your case even if the judge thinks you are wrong.
There’s a tension, of course, between wanting to seem reasonable and stay on the judge’s good side, and wanting to pursue even those parts of your case that the judge has initial doubts about. You have to make a judgement about that: sometimes making some concessions is undoubtedly the right thing to do: see this previous post. But if the judge doesn’t seem to have a good side – or seems to have taken against you on sight – and you are convinced at an early stage that you are going to lose whatever you do, then you might as well stand your ground.
In particular, if you concede instead of making the judge do his or her job and make the decision, it will be more difficult to appeal even if the judge was wrong all along.