The All Creatures Great and Small Christmas special is the year's most moving festive watch

Around half the crew have been lost, which means there is a chance he could still be alive. But there's also every possibility that he's dead.

"It's a horrendous time for Mrs Hall," said Anna Madeley. "It's every mother’s worst nightmare. And this happens right before Christmas, when Jimmy's birthday is also coming up – a time when you desperately want good news and for everyone to be together."

But the reality for her – and countless others as the war escalates – is quite the opposite.

On hearing about the devastating attack, Mrs Hall remains stoic and busies herself with peeling potatoes for dinner. If you didn't know what had happened, you might think she was just feeling a bit downbeat and not reckoning with the thought that she might never see or speak to her boy again.

But as she turns to fill a pot with water for the spuds, her shoulders sink and her head bows. We don't have to see her face to know that keeping occupied will not insulate her from her grief – and the more she tries to avoid the subject, the more the weight of her sorrow bears down on her.

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In a later scene, Mrs Hall grips one of the kitchen chairs while her eyes are fixed on the newspaper before her. It's unthinkable, but she must scan the list of confirmed casualties within its pages in case Edward's name is among them.

Fortunately, it isn't, and her hope burns a little brighter as she is spared in that particular moment. But it isn't long before that feeling is once again extinguished.

The next morning, she receives a letter – and it's from none other than her son. As Mrs Hall begins to read its contents, relief flashes across her face. He's not only alive, but he's lucid enough to have written to her, or had someone else pick up a pen for him.

But in an instant, her expression shifts.

The letter was dated eight days before the attack, which means his fate is still unknown, a realisation that proves too much for Mrs Hall. Unable to contain her anguish, she takes herself off to the calm of the shed, where a fox who was brought to Siegfried for treatment has been coming and going.

Mrs Hall has been feeding the creature dog biscuits and allowing it to hunker down in a hutch, which the vet would absolutely not approve of if he knew. But in her precarious emotional state, Mrs Hall can't help but feel for the fox, especially when she discovers the animal has sustained a nasty dog bite.

After lecturing her on the importance of maintaining a distance from wild animals to avoid such mishaps, Siegfried announces that the kindest course of action would be to put the fox down.

"No!" responds Mrs Hall. "No, you can't do that. And why should you get to decide?! He's one of God's creatures. Why should you get to decide if he lives or dies, whose life's important enough to be saved?!

"That's not right, that's not fair. You shouldn't, you shouldn't..."

It's an uncharacteristic outburst, but she is, of course, talking about her son, who has come to be symbolised by the vulnerable animal, whose fate could also turn either way.

It is a stroke of genius from writer Jamie Crichton to use the humble red fox, a persecuted and much maligned creature, as a vessel for Mrs Hall's hope and pain.

Whether it's magical thinking or something far less theoretical, she cannot bring herself to let the fox go because, in this moment, it is all that Mrs Hall has to hold onto as she awaits news of her son, not knowing when it will arrive, or what said news will be.

But while All Creatures Great and Small hasn't shied away from the horrors of the war, this is a Christmas special, which means it is joyous news all round.

Just as Siegfried informs Mrs Hall that the fox has made it through the night, and may even have turned a corner, Tristan bursts into the shed.

There is a long-distance call waiting for her.

Mrs Hall then runs into the hallway, gingerly approaching the telephone. She then hesitates, before picking up the receiver, knowing that what happens next could rip her heart right out of her chest.

"Happy Christmas, mam," says Edward, words which Mrs Hall can't quite believe she's hearing. He is injured but, crucially, he's alive and on the mend in a hospital in Singapore, news which is greeted by a tidal wave of emotion from Mrs Hall, played beautifully by Madeley.

"Merry Christmas, son," she cries as she's embraced by her Skeldale House family following days of torment.

But it's not all good news...

On mention of the prized goose as Christmas Day suddenly finds itself back on track, Siegfried remembers that he has forgotten to collect it.

"I'm incredibly sorry, Mrs Hall, it totally slipped my mind," he says, eyes scrunched in frustration as he raises his hands to his face.

"It doesn't matter," she smiles. "Nothing matters, not today."

And what could be truer than that?

After the death of my auntie Julie earlier this year following a cruel and protracted illness, those simple words, which encapsulate the spirit of All Creatures Great and Small, resonate with me now more than ever.

Jules appreciated the simple things, which are so often the best and the most nurturing, even though we all have a tendency to forget as life sweeps us up in its currents.

But Jules never did. She understood the true value of those moments – that they're not about where you are, as much as she loved soaking up the sun in warmer climes, or life's frills and embellishments, even though she did really look forward to her post-Christmas dinner cheese and crackers.

Those moments are about the people who enrich our lives and occupy a permanent space in our hearts, whether that's immediate or chosen family, and the friends we make along the way.

And All Creatures Great and Small celebrates that in abundance. As I wrote in a piece earlier this year, it is about community, centring on ordinary, kind-hearted people who are doing their bit, and not for any personal gain, but for the welfare of their loved ones and neighbours.

There is no more important Christmas message than that.

All Creatures Great and Small seasons 1-5 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.

If you're looking for something else to watch, visit our TV Guide or take a look at the rest of our Drama coverage. For more from the biggest stars in TV, listen to The Radio Times Podcast.