-WHEN all through Downton not a creature was stirring, not even a-' no, wait!

Good God, it's a camera crew! A stocky man strides into the darkened library. "You're in shot, man!" barks the Earl to a crouching figure. "This is the Christmas special, you fool! Do you want to ruin it?"

But don't worry, it won't be ruined because the Crawleys are used to this sort of kerfuffle – after all, they survived the upheaval of the war and all those beds and bandages everywhere. And it's been two series, so they barely notice the lights and the cables now. They've learnt to ignore the cries of "Action!" and the tantrums of the flustered fellow with the folded sheaf of papers who calls himself the floor manager.

After dark, to relax, they sit on baking pans and push themselves up and down the rails the crew laid across the hallway (hence the phrase "panning shot"). They like to fall off halfway over, smashing into the wooden banisters of the enormous staircase and screaming "Aviva! For life's little emergencies!" before rolling around on the floor laughing.

But they didn't all adjust so well to having their lives filmed. You won't be surprised to learn that the Countess took a little longer to adapt to the requirements of modern filming.

"Young man," she said over her spectacles one day, to the sound technician who was holding a boom microphone above her head on the chaise longue. "If that contraption so much as touches a single feather of my bonnet I shall have you sent to the Front faster than you can say "Tipperary". Now, we have a commercial break coming up. Raise it another foot like a sensible fellow and let's get on with it, shall we?"

There is huge speculation about tomorrow night's episode. One of the chief problems faced by writer Julian Fellowes was finding anyone who hadn't fallen in love with anyone else. His solution is ingenious. Given that the house itself is as important as the characters – after all, the programme is called Downton Abbey, not The Crawleys – he has let Cupid's arrow fall on the furniture too. Tomorrow night will see the Earl's grand piano fall in love with the parlour maid's humble, wooden bedside stool, whose tender performance is sure to secure it, forgive me, an Emmy for Best Chair in a Supporting Role. Enjoy – and Happy Christmas.