NOT many people know this. Every winter, when Stourhead House is closed to the public, the volunteers run special tours into the back passages of the house while it is being cleaned and the conservators move in to do their work.

The tours are free (although you have to pay the £17.50 admission to the house) and provide a fascinating insight into the colossal work that goes on just to keep the house going and its contents preserved.

Today is the first of 44 days when the Behind Closed Doors tours operate over the five floors of the house, including the servants’ quarters in the attic and the below ground storerooms.

Three tours run on most days through to March 8. Booking is essential by calling 01747 841152 and groups are usually up to 15 for each tour. Shaftesbury Tourism accompanied four members of the British Guild of Travel Writers on a visit last year, and this is what we found….

ONLY one of the five floors of Stourhead is open to view during the year, the ground floor. Nobody can see the vaults, where the stores were kept, or the kitchens under the ground floor. Nor can they venture upstairs to the bedrooms and, beyond that, the servants quarters in the attic.

There are a number of reasons – the staircases are narrow and steep; many rooms are used as storage and are unsafe; it’s a mass of wiring and pipes; and the furniture that survived a fire in 1902 is only really enough to fill one floor anyway.

But until early March, the National Trust does open up these floors (and a number of closed off areas in other NT properties) so that enthusiasts can get a real feel for the house, and an understanding of the work that goes in to keep the house afloat and open to the public.

It’s also when the conservators move in to repair, check and restore. On our visit, two were at work checking all the ceramics for wear and tear/damage. The library was also off limit as there was work being carried out using scaffolding.

Each item of furniture in this time is protected with its own bespoke, numbered and named cover. The important items have an orange sticker. “It there is a fire, we get them out first,” says Robert, one of our two guides.

You learn how the house is under attack, from the weather, age – and insects, like wood lice and woodworm. The roof is now heated to melt any snow which may accumulate and cause damage. A computer now governs the biomass boilers, which turns off the radiators if the rooms are too dry, or turns them on if too damp.

So the moisture in each room, including the 20 rooms at the top for the servants, is constantly monitored.

We also learn how life was back in the day when the family lived there. How the staff had their own staircase, so they wouldn’t meet the owners. And if they did, then how they were instructed to turn away and not catch the eye.

In keeping with the Upstairs Downstairs theme, the maids’ rooms upstairs had a balustrade outside the window so that they couldn’t look down on their masters on the lawn. The only room in the attic with a fire was for the senior maid – the house consumed three-quarters of a ton of coal daily, and all that and the water had to be carted upstairs.

In the lowest floor, the storerooms, the barrel run for deliveries of beer is still there. So too the hooks for hanging the game birds and meat, the dairy and wine racks. And it’s all seen in an hour.

Go see: it’s fascinating – and enjoy this video shot by one of the journalists, Geoff Moore, on his visit.