Think of Big Brother and several things might spring to mind: Jade's philosophising, Nadia's nicotine cravings, Nasty Nick's scheming or the first green shoots of a blossoming love affair between one of Big Brother's numerous couples. But before long, without fail, one person will crop up, the one constant of an ever-evolving show, the Big Sister herself: Davina McCall. Here she talks all things Big Brother, including why she was nice to George Galloway, why she loved last summer's series so much, and how she might end up giving birth outside the Big Brother House

So, another Big Brother, another pregnancy. What is it about you, Big Brother and babies?
I'm trying to think of things to put on the T-shirt. I'm going to do the Big Mother T-shirt and I'm trying to think of things to put on the back. The best thing I've come up with so far is 'The Trilogy'. Can I tell you something really tragic? When Matthew and I decided that we might go for another one, I did plan it so I don't actually give birth during Big Brother.

That would take reality TV to new heights wouldn't it?
It would take it too far! However on the last week - as it's a bit longer this year - I will be taking my birthing bag with me to Elstree, because I'm having a homebirth which means that I can give birth wherever I go. If I've got the birthing bag with me, I could be giving birth in my dressing room. You won't actually get to see the birth but it may happen at Elstree.

What did you think of Celebrity Big Brother this year - it was quite spectacular, wasn't it?
What I thought was really lovely about Celebrity Big Brother this year was that it wasn't just a tabloid's dream, it was also a broadsheet's dream and that's what I quite enjoyed - the fact that finally people outside of the normal sphere of interest were sitting up and going 'Actually, this is fascinating!' It's not just about voyeurism, it's watching how people interact with each other and how people deal with social situations, and it is fascinating.

Some of the people in Celebrity Big Brother behaved pretty badly. Did you find it difficult to be civil to some of them when they came out?
If they have been a good housemate, if they've been great to watch - coupled with the fact that we really appreciate them going into the house in the first place - a complete character assassination is never going to be on the cards. As much as I might personally dislike someone, it's not right for me to completely annihilate them.

George Galloway was a good example. People were baying for his blood. When he was evicted, I had so many messages on my phone asking me to lay into him. But he's a human and he did do the show, and he enjoyed quite a good ride for the first few weeks. Then he began to do a bit of the bullying and people's opinions changed. I've got to give him a bit of a hard time but I can't completely lay into him, it's a bit cruel.

Do you have favourite housemates?
There have been very, very few people that I've disliked on Big Brother, but I haven't loved everyone. Lots of people found John McCririck hard to swallow but I just thought he was brilliant. And even though some of the things he did were difficult to live with (like the way he wore his pants) as the presenter of the programme I thought he was bloody brilliant. So even when the public opinion on someone might not be that great, I'll think that they're great because they're a fantastic housemate. Makosi was a brilliant housemate - I applaud her for that, and I did thank her in her interview.

Last summer's Big Brother was also a spectacular success, why do you think it worked so well?
The production team have now got it absolutely down pat with what we're looking for. Rather than looking for stereotypes, they look for big personalities. So that means we could have three or four gay men in the house because they're brilliant personalities. Or we could have four blonde girls with big boobies in the house because they're really, really fun. Also we can put people in and think they're going to be a nightmare or they're going to be tricky to look after, or they're going to be very demanding, but when they get in there they might be completely different. Because of free will, you've got absolutely no idea what people are going to do, or how they're going to behave.

What were your favourite bits from last summer?
I found the whole Craig and Anthony relationship fascinating. I think that Anthony won that programme because he just took that so well and I also feel that the nice guy always prevails. Science annoyed the hell out of me when he was in that house, but when I got to interview him I wondered why I didn't see more of that side of Science. I think he was with people who didn't bring out the best in him.

But I loved Derek. To have somebody who blows all stereotypes out of the water, when they are every single stereotype under the sun, was amazing. He was hilarious, and also very true to himself. My favourite thing about Big Brother is that you can't judge a book by its cover - you can decide someone's fate the minute they walk in, and then you change your opinion of them. Also last year we had my favourite task of all time - the cardboard box task. I've never laughed so much in my life.

Do you think that'll be making another appearance this year?
We've already done it twice, because it was done again in Celebrity Big Brother. George Galloway really annoyed me during that because he started a sort of communism group movement to get out of the boxes. That really pissed me off because the Americans wanted to stay in there and win - because that's the American way - but everybody else saw that as a negative thing, so they all got out, which was really annoying.

Do you find it difficult to keep Big Brother stuff a secret?
No. I feel extremely passionate about the rules of the programme and the impact of the programme, so I think if somebody found out who was going in beforehand it would ruin it. For me, keeping those kinds of secrets is easy. Keeping the fact I was pregnant was a bloody nightmare! It was such good news I wanted to tell the world!