Noughts + Crosses starts Thursday 5 March on BBC One

Helen Baxendale plays Meggie McGregor in Noughts + Crosses.

What drew you to the role of Meggie McGregor?
When I told my children what character I was up for they gasped, so I knew this role was great. Within the scripts and the book Meggie is very strong and warm, she is a real mum, she gets on with things and she wants the best for people. All of these terrible things are happening in this awful world around her but it doesn’t stop Meggie from being loving and kind but also firm. She is a multifaceted character. She is not overtly political in that she is just trying to get through her day and she is a survivor in every sense of the world.

Meggie wants what is best for her family and so she tries to work within the system to do the best for all of their lives, but she doesn’t see change coming any time soon. She sees the destructive elements within violent resistance and so she has made a pact with her husband, Ryan (Ian Hart), that they won't involve themselves in that anymore, for their kids.

Now her youngest son, Callum (Jack Rowan) has a chance to do something different at Mercy Point, by becoming one of the first ever Nought cadets allowed in the academy, and she is very supportive because she sees it as a new start, a chance to do something different.

Tell us about the role race plays in this world and this story. 
This alternative world is reconfiguring history and is purposefully difficult to get your head around. I shot a scene where someone opened a door for me and I got out and said thank you but then I realised the person who was opening the door was black and the way I went through that door was not sufficiently deferential. There was something in the way I went through that door which was equal, which is wrong within this world. Even tiny interchanges like this are affected by hundreds of years of what we accept.

I would go through a door in London and I wouldn’t think twice about simply saying thank you, however, if you are an oppressed minority and someone opens the door then that interchange is different. It is moments like that, which are quite hard to grasp. There is still vast inequality everywhere you look in the world, and this drama is about race but it is also about the subjugation of anybody and about inequality.

There are eye-opening moments filming this show, like when I was apologising to the costume department as I only had a black bra to wear under my costume but they told me that it was perfect as in this world there would only be black bras because they are made for the Crosses.

How does your character bridge the Nought/Cross divide?
Meggie bridges both worlds, that of the Noughts and that belonging to the Crosses, and as their housekeeper she is actually quite high up in the Hadley’s household. Whilst she doesn’t have airs and graces it is clear, when coming back into the Nought world, that she has learned a particular way of speaking.

Two generations ago my family were working class and some of them were working as staff at big houses, so moments in this drama are relatable for me.

The McGregors are poverty stricken but they have a hell of a lot of pride - you keep your house immaculate and you dress well, so I wanted Meggie to be proper. We are poor but it is really important that we are not broken.

Meggie is very aware of the constraints of society and she knows that they won't be broken for a long time, but within that you can lead a decent life with hope and joy. She sees that her home is warmer and more functional than the Hadley’s house, and that actually money and status do not matter. In fact, she understands that a lot of those things don’t matter, but she does also want chances for her sons, which is why Mercy Point is so important to her.

For Meggie, the ceremony at Mercy Point, where Callum is sworn in, is a moment of pride and joy. We filmed this outside in an amazing location in South Africa and the sun was beaming. We, the Noughts, got to dress up and go on equal terms - almost - with the Hadley’s and the rest of the Crosses, because we are parents of a cadet. It was an amazing moment to film and we had some incredible African dancers performing.

Tell us about Meggie's friendship with Jasmine Hadley.
Meggie is aware of Jasmine's failings, but she likes her and she sees her strengths, and the fact that she has stayed with it and is herself a victim of the system. Jasmine is fun and naughty and has a spark despite everything. They're two women form opposite ends of life but they've been with each other a lot, thrust together and there is solidarity among women which is great.

Meggie does bind the two families and maybe, when Sephy and Callum were young, she might have thought of what it would be like if they were together, but casts it from her mind as absurd and dangerous. But she knows both of them and loves both of them and realises it isn't an absurd notion - but it is dangerous.

How did you switch off and step away from Meggie at the end of a day's shoot?
I used to try to carry the weight of my character around with me, but I just can’t do that now, it's too hard. Of course you come back after a long day and are heavy hearted when all of your scenes are unremittingly upsetting or angry, but I don’t take it home with me. I'm too old for that and it is exhausting. I have to enjoy life - it is a privilege to be an actor and I love what I do, so I will act those moments and then do my best to switch off - life is too short.

Luckily there are a lot of characters in this story, so the weight is shared among us all. At the heart of this tale is a beautiful love story and a sense of hope. Meggie clings on to this notion of hope, believing that something good can come out of the tragedy. She thinks she has been part of the problem and she feels like she can do something to redress the balance. So she does.