Are There Any Questions That An Interviewer Cannot Ask Me During An Interview?

Whilst an interviewer can ask quite a lot of constructive questions during an interview, there are actually some questions they just cannot ask. This is because there are certain laws which do not allow interviewers to hire employees on certain grounds. So, for example, interviewers are not allowed to ask you any questions regarding race, religion, national origin, your age, your family status or your birthplace. If they do it is illegal and you can report it. It could be that the employer has a prejudice against a certain religion or they may hate people from a certain part of the country. If that is the case, if they did not employ you on those grounds it would be discrimination and that is illegal.  
However, saying that there are certain questions employers could ask indirectly such as "are you a UK citizen?" That would not be illegal and you should answer it as much as you can without feeling uncomfortable. Only tell the interviewer what you want them to know and remember that the interviewer may not necessarily be being discriminating on purpose.

They also can't ask you any questions about the logistics of how you could do your job.  Such as childcare arrangements.