To ask about flexible working hours at an interview?

If you can't do the job if there is no flexibility I'd expect you to ask about this at the interview and am surprised you didn't do so before hand as the interview is a waste of everyone's time if there is no flexibility.

I'd mention it before the interview. Definitely not after

Most employers wouldn't let you not take a lunch break, it's a legal requirement.

If you got offered an interview I'd mention it then

I would wait until being offered the job. A 20min lunch break is a legal minimum for those hours.

Some employers discriminate: harder for them to do that after an offer.

Ask after. If the employer offers you the job, that's the time to negotiate flexibility, pay etc. You can ask before but unless they're incredibly flexible and it's something they promote, then it could go against you in the decision process (it shouldn't but I've seen it happen).

Once the hiring manager has decided they want you, they're much more amenable to negotiating stuff like this (unless the job has specific core hours where you need to be present).

I think if you're planning on working over your lunch break they may not be able to agree to that as there's legal limits on time worked. Dh got (mildly) told off for regularly doing that.

Yes don't wait for an offer, it would be wasting everyone's time if you then said you couldn't do the role. It should not harm your prospects at an interview to discuss this - if they really like you they may decide to offer flexibility where they might not have previously considered it.
As an recruiter I would much rather this type of matter was raised early on so we can manage expectations and have time to fully consider it.

Agree with Surrey "Some employers discriminate"

Except I would change it to "lots of employers discriminate".

Could you ask for an informal visit and raise the subject then? Most offices need cover for the whole day to ensure clients can contact the office etc but I guess it very much depends on the role and size of office.

And if y ou ask for flexible hours remember they may require more flexibility from you.

You could ask about core hours in the interview, this might give you an idea of flexibility. Where I work core hours are 10-12 and 1-3 although there is flexibility within that too

If you really want the job I would go at it the other way around - start looking at how you will manage if you are offered the role and get the childcare in place if possible.

Agree re informal visit or phoning them. They either will have some flexibility or they won't.

id be very annoyed if someone dropped this on me at offer stage and even if we could accomodate it (doubtful or we'd put it on thd advert to open up another candidate 'pool') it wouldnt start the relationship off on the best footing imo, especially as working hours are discussed at interview stage (unless its a poor interview)

it would bd very easy for them to withdraw the offer with no risk of discrimination, especially if they covered working hours at interview

I think you could drop it in in a general question about terms and conditions and benefits.

However, it isn't strictly legal as you should have a 20 minute break if you work over 6 hours. I have an informal arrangement similar to yours as I work a 6 and a half hour day but usually work through so I can finish for the school run. It benefits both of us though as they don't want me to drop any more hours and I'd rather have the extra salary and skip lunch break. I still eat lunch and usually nip to the canteen to buy something and eat at my desk, but that takes no longer than a comfort break or going to get a tea from the machine etc (or a smoke break).

I'm in your position OP and have an interview this week. I wouldn't say anything at interview and if you're offered it then you're in a stronger negotiating position. If they say no and you can't do the job then you just turn down the offer. If they want you they are more likely to say yes!

If it's a non-negotiable, I'd bring it up at interview because you've nothing to lose. Ie, if it puts them off giving you an offer when you otherwise would have got one, it's no skin off your nose. If you really wanted/needed the job and it was a nice to have, there'd be an argument for waiting until an offer, but as that's not the case you may as well be open.

I have always made my need for flexibility clear in interviews, and basically explained that there are only certain conditions under which I would be able to do the role, and it's served me well. If for whatever reason the role won't be suitable for me because of my family commitments, better to know that sooner rather than later.