Homes & Antiques caught up with the oracle of Downton Abbey (as he's referred to on set), historical advisor Alastair Bruce, to find out what went on behind the scenes…

His interest in interior design came, he says, from visiting relations in extraordinary houses and being fascinated by how beautiful they were. 'I learnt a lot about the golden mean (Aristotle's theory of the 'desirable middle') at school, and about how classical buildings were constructed so that you could divide them into threes and fives to create perfect proportion, something that is important to English architecture now,' he says. 'Interiors have fascinated me since then.'

Find out more about Highclere Castle and its history here.

You might also like antique tiaras sparkle in the upcoming Downton Abbey movie

The ancestral paintings in Downton Abbey

My favourite items are the dining room paintings already within the house. They are a fine collection of aristocratic art that tells a story of a great family and all of them are rather beautiful. It filled me with delight that the cast took such care in everything that surrounded them – it was lovely.

Decorative props used in the filming of Downton Abbey

We needed a leather place-card holder with the Crawley family crest on it at one point, where you clip the names for where people sit on the table. I described it to Donal, who is the production designer, and he got a lovely one in green leather, which you can see when Neville Chamberlain comes down for dinner with the family. The Dowager Countess gets in to set the table and she would normally sit a long way from her cousin Neville, but we used this place-card holder to tell the story that she moved her seat and, thus, her position. This played a leading part in the episode.

You might also like inside the real Downton Abbey: take a tour of Highclere Castle

What challenges did you come across in filming the final series of Downton Abbey?

The most important thing was to make sure no one relaxed, otherwise they take themselves out of the period and it was not a relaxing time. For example, with the weddings, most people don’t have the same church-going instinct that they used to. Men wear hats to churches but, of course, Christian men of that time would never dream of doing this, nor would a woman walk into a church without one. When people wore hats they wore gloves, so I had to make sure all these details that are vitally important were correct.

You might also like Downton Abbey star Michelle Dockery shares her favourite music