It is always worth paying a bit of attention to the more obscure bits of the ET3 form.
This is the form the Claimant gets back from their employer, after they have sent their ET1 to the tribunal. It sets out the employer’s response (subject to their drafting skills).
It is easy to focus on Paragraph 5, which is the main section. This is important, but make sure you look at the other parts too. These will tell you, for example, whether they accept the claimant’s employment status and if they dispute her working hours.
If one of these, more peripheral, issues are going to be argued, it is important to realise that as soon as possible. And, if the employer has said that they are not, but later tries to go back on their statement, it is reasonable to point to the ET3 and ask why they have changed their position.