John Simister: P&A Wood – Guardians of the vintage Rolls-Royce and Bentley

Not the model that many of us owned, obviously, but the real, actual car with its YU 3250 number plate. Automotive iconography gets no better than this, especially when behind it in the picture is AX 201, the original 1907 Rolls-Royce Silver Ghost that, when new, drove from London to Glasgow many times to demonstrate its reliability.

This is automotive royalty. A few weekends ago I visited P&A Wood at its base in Great Easton, just north of Great Dunmow in Essex. It was a guided tour with friends from the Singer Owners' Club, although only two crews actually arrived in Singer cars: a pre-war 1½-litre sports tourer and a 1960s Gazelle. I drove there in my Sunbeam Stiletto, a close relative of some Rootes Singers and by far the smallest car on the P&A Wood site that day.

Twin brothers Paul and Andrew Wood set up as specialists in mature Rolls-Royces and Bentleys in 1967. They began in Moreton, Essex, with Paul doing the coachwork and handling sales, Andrew in charge of the engineering side. In 1970 the growing business moved to Great Bardfield, grew some more and in 1988 landed on the current site. The Wood brothers built a new engineering workshop and in 1995 added a new, but period-looking, two-level showroom. 

Today P&A Wood employs 65 people, the brothers continue to do what they enjoy the most and Paul's daughter Georgina is the company's managing director (and a Brooklands trustee). The place is full of very valuable Rolls-Royces and Bentleys of impeccable provenance, considerable age and frequent uniqueness, but I'm pleased to see a surprising number of Silver Shadows and their descendants awaiting attention, too. These are not greatly valuable nowadays, and indeed some have descended into something approaching bangerdom, but not those at P&A Wood. Here, they are administered to in the way their maker always intended. 

One of the long-serving craftsmen, Keith Potter, takes us round the various buildings. We begin in a storage area which had been the coachworks, and which is soon to be converted into a service bay for recent Bentleys with a machine shop behind. Andrew Wood's Merlin V12 aeroplane engine sits in here, never flown. Upstairs, where engines are built, is a machine for testing lever-arm suspension dampers so they can be calibrated (by changing shims within) before fitting to the car. 'We rescued it from a skip,' says Keith. 'It's the only one left in the world.'

Now we're in the main workshop, choc-full of cars owned by customers who will often have several, and who want them all to be in perfect working order even if some are hardly ever driven. Here's a 1908 Silver Ghost, registered R 562 and featuring silver-plated brightwork. Known as 'The Silver Dawn', and thus previewing a later Rolls model name, it's one of P&A Wood's most famous restorations.

Next, I encounter R 1075, a Rolls-Royce 'Experimental Speed Car' known in R-R circles as '1701', which in 1911 drove from London to Edinburgh and back entirely in top gear. It and 15 other Rolls-Royce contemporaries repeated the feat in 2011 in a centenary celebration.

A 1921 car – the first Rolls-Royce model with full pressure-fed engine lubrication – is nearing the completion of a rebuild. It has higher-compression pistons, specified by some owners to give more power, but Keith rues the reduction in the signature silken smoothness. Nearby is a rolling road, used not to measure ultimate outputs but to check everything is working after major work. 'We tend to use it for the older cars,' Keith says, 'especially on a wet day.'

Now upstairs, where is garaged Paul Wood's 1901 Decauville. It has just returned from a test run ready for the upcoming (and now past) London-to-Brighton Run, and the type has a place in Rolls-Royce history too. 'Henry Royce started out with Decauville,' Keith reveals, 'but soon he thought, "I can do better than this." ' 

We enter the trim shop further along on the same floor to be met with the extraordinary sight of the Rolls-Royce Phantom III that 'Monty' – Field Marshall Montgomery – used during World War Two when in England. It's extraordinary because its first owner, Alan Butler of aircraft manufacturer De Havilland, commissioned from coachbuilder H J Mulliner a body whose windscreen sloped forward. Apparently, there were aerodynamic advantages to be had from this. P&A Wood restored this almost surreal machine, which won its class at this year's Pebble Beach Concours.

Beyond the Phantom, apprentice Ellie – one of eight learning the crafts of car restoration – is reconstructing a seat's frame, springs and other innards. She has a year to go on her course and naturally hopes to have a permanent P&A Wood role afterwards. The whole area is rich with hides, wood veneers, gimlet-eyed attention to detail.

On the way down to the paint shop, we pass the doors to the boardroom, fine pieces of carved wood formerly resident in Rolls-Royce's old London office in Conduit Street. In the paint shop are spray booths with peel-off wallpaper for when the overspray gets too much, cars having their contours fine-tuned with polyester primer-surfacer, others about to get their top coat – two-pack paint if a whole new job, maybe cellulose if it's a repair to a car which already has a cellulose finish elsewhere.

Further along is the panel shop, where sheet steel or aluminium is shaped from scratch, where the deep body rebuilds happen. 'We always put weights in the cars to represent the mechanical components when we're setting the panel gaps,' says Keith, pointing out how the gaps in the finished car could be wrong if this isn't done.

We next find ourselves in a very new, but again period-looking, showroom built in 2014 to house the part of P&A Wood that sells brand-new Rolls-Royces. So the marque's entire history, through all its convolutions, is represented here. There is no such official representation for brand-new Bentleys but, says Keith diplomatically, 'We can supply one if a customer prefers to deal with us.' 

Another showroom displays parts and accessories ancient and modern in intriguing juxtaposition. And then it's time to leave. I'm about to depart in my very small Stiletto, a car humble in such surroundings, when Paul Wood (in overalls, clearly in the middle of restoring something) walks up. 'That's a really nice car,' he offers. There, transcending all the automotive aristocracy everywhere evident speaks a proper enthusiast.