which line in immigration control?

I'm preparing for my first trip with my new born who has both her UK and US passports.  My question is which line do we get in when we return to the UK?  I know we have to enter with that passport for her but since I only have an American one do we get in the non UK passport holder line or the other?  (will be flying into LHR). 

Also what if I was also flying with my husband and stepson who only have UK passports?  I think they want families to stay together so would we all go through the US line in America and the UK one in England regardless of not everyone holding the correct passport?

TIA!

Always ask - it can change anytime and honestly in my experience it depends on the person.

We we travelled as a family (3 UK and1 US) they had us go thru NON-EU here in the UK but on the US side they came thru with me on the US queue.

Ask ;-)

Ok thanks Chilly willy!

We just choose whichever line is the shortest. Once about 10 years ago my husband and I went through on separate lines and the IO made me leave the line to go and find him, it took us ages to get through. Now, with myself and the two kids all holding different passports, we just choose the shortest line and head towards that one. I find the people who are shepherding people through to the IO's desks don't really know what to advise us, so we just do what we think is right. Good luck!

Do you have a spousal visa or ILR along with your American passport?  I always stay with my husband and go to whichever line is shorter, they take me at either line, with both spousal visa and ILR.  I plan to continue this when our baby is born and she will have both UK and US passport-- but can only use the UK passport here.

In the US, he always comes along with me in the US line, the non-US line at Newark is always long and slow!

Go through together and always ask is what we always do, will be doing so in a couple weeks at Logan.

Thanks for the advice everyone!  And yes, I do have a spousal visa.  It will only be me and my daughter on this trip though.

I never even considered I'd be able to go through the EU side when I traveled with my son and went straight to the Non-EU line where the line was suuuuper long. Luckily, one of the people directing everyone asked me after I got in line if my son had a UK passport and when I said he did, he directed us to the other line, which was much shorter and quicker! I've traveled once with him since then and went straight to that line again, no problems whatsoever. This was at Heathrow.