“There’s a lot of mess and paint in here,” warns my guide, Claire Mann, as she prepares to usher me into the hallowed space.

She’s not wrong there; the place is plastered with chalky white dust, there are blob-covered rafters, long-hardened red and green on the walls; even the computer mouse is pleasingly marbled in blue, purple and white.

Dimity, Dead Salmon and the delightfully named Clunch, indeed all the company’s 132 famous colours, start on the gallery as china clay is taken from its bags and tipped into vast mixing vats to create the all-important base.

Then, in a scene which really does resemble Charlie’s chocolate factory, the mixture is whizzed through the pipes and down into the colour-mixing vats on the factory floor.

White, black or Middleton Pink, all Farrow & Ball’s paint is made from four colours, expertly blended – sometimes to very old configurations – in these vats.

Today they are making Pointing, the delicate white tone which is probably their best-selling colour although Elephant’s Breath – a soft grey – has so many fans that it even gets mentioned on Mumsnet.

Why do people love them so much?

Is it because of the wacky paint names the service – you can ring up and a nice lady or chap will give suggestions as to which colour is best for your front door – or the finish; that velvety, deep effect?

All, probably.

The reason their paint is so appealing, says Claire is because “We use the best quality ingredients and a lot more pigment than most other manufacturers.”

They were started by John Farrow and Richard Ball during the 1930s, supplying paint to the Admiralty and the War Office and the company’s fortunes were revived by entrepreneurs Tom Helme and Martin Ephson, who later sold the company to the venture capital firm which owns it now.

Despite some modernisation – computers are employed to help ensure colour accuracy – the Wimborne factory is pleasingly old-fashioned.

There is no swish and glide of computerised machinery, what you do hear is the swoosh and glug of paint being mixed, the rattle of tins, the thunk of lids being attached to those iconic brown and cream cans and the shout of the employees – it’s delightfully noisy.

All paint is weighed before leaving, to ensure accurate amounts and the only real sciencey bit is in the quality control area where they sample each batch to ensure the match is correct.

Here they paint black and white cards to check for coverage and each batch is monitored through a colour spectrophotometer to bring it as close to the desired formula as is humanly possible.

“Most manufacturers work to a one per cent difference,” says Claire. “We work to half a per cent.”

Amazingly they only manufacture three colours at any one time, working out how much to make through their computerised order system.

From here their paint is despatched to Japan, to Brazil, maybe even to the White House or Buck House; Farrow & Ball paint is thought to have been used on both.

Of course it’s not just paint they produce.

Next door is their wallpaper division, yet another fantasy factory where papers are prepared with the 70 ‘ground’ colours, paint – they don’t use cheaper ink – which are put on with two mechanical brushes to give that handpainted look.

There is a lot of hissing, whooshing and crackling as the paper snakes its way through the various rollers, which create the three styles of pattern which Farrow & Ball produce.

Patterns are created either by roller, a flatbed stamp, or by dragging which results in gorgeous stripes.

The papers are dried between processes, glazed to preserve the patterns, and several metres are rolled through before the all-important Go! sticker is applied by the operator, to tell the person at the end when it’s good enough to start trimming and cutting a ten-metre roll.

Much of the paper is recycled, either to be pulped or is given away to charities and school craft projects.

Staff are also welcome to take away little pieces and many are proud to show off how they have transformed them into crafty creations.

For a price the company will make your own wallpaper for you as, indeed, you can apply to have your own paint colour mixed and Name It Yourself!

I drop a large hint that a paint called Faith might be a good idea, as in: “I think you should call a paint after me,” but I know I’m lucky to even get this private tour.

If you want to follow in my fortunate footsteps and make a difference to children with life-limiting conditions, there is a way; click on to farrowball.com/juliashouse between August 19 and 23 and place your sealed bid for your own Grand Tour of this marvellous place on September 6.

You’ll love it.