Lily’s delighted Ethan’s withdrawn his resignation and this weekend Casualty fans will see the two doctors work well together in a difficult family-patient situation. Could they be the new ED dream team?

Casualty star Crystal Yu sheds some light on why Lily and Ethan are a good match and also reveals why this is one of her favourite Casualty epsiodes…

What do you love about Lily and Ethan’s ever-changing friendship?
“I’ve played Lily for almost three years now and seen her and Ethan develop so much. Once upon a time she would have liked to be with him, as he understands her, but now she’d rather they were great friends.”

How does Ethan understand her?
“Lily’s one of those people who doesn’t explain herself very often. She feels if she has to explain who she is to you, how can you be her real friend? Ethan (George Rainsford) gets that. Yes he was angry with her for how she treated Alicia (Chelsea Halfpenny), but he also understood why she did what she did.”

The Alicia-bullying incidents were fuelled by Lily’s sudden loss of her father. Is there more to come with this storyline?
“Lily’s still grieving. She thinks the only thing she can do is keep moving forward (she’s now a registrar). But I think, at some later point, she could crack because she hasn’t grieved properly over her father’s death.”

How might this manifest itself?
“I don’t know, I’m just guessing and we haven’t filmed anything, but I hope down the line it will come crashing back. Perhaps around the anniversary of his death, as the anniversary of a loved one is a very difficult time. Casualty is very good at setting up plots and journeys you can go back to.”

In this week’s episode, Ethan and Lily work well together to help autistic patient Sash Gilbert. What can you tell us?
“Brilliant young actress Sophie Henderson joins us for this. She’s done some theatre but never worked on television before. She has autism. Our director Jo Johnson did a fantastic job of casting her as Sash, as Sophie is absolutely brilliant in the role.

“Diversity is always talked about, but it’s not only about race or skin colour – it’s also about ability and disability, and representing the world as it is, on television. I think we need to do more!”

Casualty is already excellent at natural race and gender representation…
“Definitely. I feel that with Lily. She’s not a ‘Chinese doctor’. She’s a doctor who happens to be Chinese, if that makes sense.

“It’s important we see people for who they are. For example, with Sophie’s story. Hopefully it allows people to understand what autism is. The spectrum is so vast; it’s not just Rain Man! Autism is a label for what that person is going though. You have to look beyond labels to see who a person is, whatever their differences.”

What’s been your favourite aspect of working on this storyline?
“Getting to know Sophie on set, working with her, and seeing how talented she is. I just know this is going to be a brilliant Casualty episode. And it’s her first television role! I wish I were as talented at 17…”

Do you remember your first television role?
“Yes! My first television experience was an MTV commercial by a director called Chris Brown – not the singer! I don’t remember much, other than I played the girlfriend.

“My first ever drama was on Dream Team when I was still in college. I remember thinking ‘when are they going to say action?’ I panicked and thought I missed it, and so I walked on set… only for them to tell me ‘Crystal, just wait for us to say action, OK?’”

Casualty’s Step Right Up epsiode screens on Saturday, February 6, BBC1 at 9.20pm