All Creatures Great and Small stars on season 6: 'We’re on a different journey to the books'

West added: "No. We’re about to have some discussions about that. I mean, one of the things that the books do is dramatise the fact that Tristan leaves. Brian, the original Tristan, left the practice. And I don't think we'll be doing that. I hope not. So at that point, I think we will be non-canonical."

Madeley continued: "Yeah, because our adaptation is so very different to both the '70s adaptation, but also how the book’s written, it's quite a different journey that we're on, even though those stories are obviously the main source of inspiration, the journey and the arc for those characters is very different. So we shall see."

West said: "It’s one of the pleasures of being in a returning series is that it feels quite like life, in that you're in it, and you try and play the part as well as possible, but you don't really know what's around the corner.

"It's not like doing a play where you know you're going to have to shoot the king in two pages.

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"The fact that we don't know what's coming in series six is sometimes a little bit, I wouldn't say worrying, but sometimes a little bit of a concern, but at the same time it has to contain the possibility of being surprised, just like life."

While we may not know much about where season 6 will take us at this point, we do know that the rest of season 5 will include the return of Callum Woodhouse's Tristan, who was away fighting in the war in season 4.

West recently said of Siegfried's reaction to his brother's return: "He's obviously changed. And he's changed in ways that I don't fully understand. He's obviously seen some horrible things which he's not talking about. And he's obviously masking with drink and good humour."

All Creatures Great and Small seasons 1-4 are available to watch on My5. Season 5 is airing new episodes on Thursdays at 9pm on Channel 5 and My5. You can order James Herriot's All Creatures Great and Small from Amazon.

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