Since the 1700s, many great painters have turned off the Great North Road, so to speak, and found their way to Aske Hall.

Rembrandt, Gainsborough, one of the Brueghels, others from the Dutch and Flemish Schools, Masters of the Italian Renaissance – a bound register describes the treasury of art arriving at the stately home near Richmond, and sometimes departing.

The house is unlikely officially to record its latest journey into the art world. Yet in time what happened there may have more significance for more people than anything that went before.

It was a simple idea, and its impact has far exceeded expectations. Bringing Aske and the A1 together inspired such a burst of creativity, the hundreds who made the detour in the hope of having it acknowledged caused a traffic jam on the drive through grounds attributed to Capability Brown.

They brought oils, watercolours, pastels, ink drawings, and almost every other medium offering a means of self-expression within a frame.

A lady arrived by taxi from Otley to deliver her creation, and a hired van brought 30 paintings from what may turn out to be the beginnings of the Rotherham School. In another case, the varnish was still wet on a seascape taking its last-minute chance in a unique regional event, whose format is based on the Royal Academy's annual exhibition.

Never before has Britain's longest road fuelled such inventiveness. The response to the A1 Open Summer Art Exhibition meant Mandy, the secretary in the Aske estate office, had to abandon her official duties to administer the convoy of exhibitors, professional and amateur. They were bumper-to-bumper in the quest for recognition as much as for the prize money and the potential sale value of their endeavours.

"Mandy was swamped. She couldn't get anything else done," said the Earl of Ronaldshay, heir to the 4th Marquess of Zetland.

His Lordship agreed to provide the family seat for the judging process because he shares the aims and enthusiams behind the exhibition. It invited entries from anyone in Yorkshire and the North-East, and attracted 1,200 works, from teenagers to an 83-year-old. The show's title draws on the A1 because of the road's historic importance to the area. It's also only four miles from Richmond, home of The Station, where the 250 chosen ones will hang.

Lord Ronaldsay's drawing room, and its Chippendale, porcelain, and soft furnishings, were almost submerged by images created in studios, stables, garages, and at kitchen tables. He didn't complain. "If there's a great piece of art lurking among all this, or if an artist is discovered and their career launched because of what's happening here, that would be marvellous."

They were given every chance. The seven judges included some of influential names in the art world. The chairman was Greville Worthington, a trustee of Yorkshire Sculpture Park and the Henry Moore Foundation, and a Turner Prize panellist. Among colleagues was Sonia Lawson, Royal Academician and daughter of the famous Dales painter Fred Lawson, collector Ronnie Duncan, who bought his first Hockney in 1952 for £12, and Dr Veronique Powell, a French art historian, lecturer at the Sorbonne, and authority on Spanish art.

"Goya is my man," she said, so you wondered what she made of offerings from Hull, Huddersfield and Hartlepool, and subjects such as Malham Cove, Byland Abbey, Leeds at Christmas, Swaledale sheep, and a Scarborough entrant's Spurn Sunburn, with its hint of Beryl Cook's influence.

"The number of entries surprised me and shows how keen people in this country are to express themselves through art, regardless of their background," said Dr Powell. "In France, art is concentrated among an elite. Unlike in Britain, there is no strong culture for amateur painting. Here I think the public's enthusiasm comes from the way the subject is taught in schools.

"Today, we have seen some very good stuff, and maybe 10 per cent that has been of poor technical quality. From the way they translate what they see, it's obvious people in Yorkshire are very fond of its landscapes, and I particularly like their use of vivid colours."

Evaluations were made in the Saloon, where an expanse of art of one sort or another reflects aristocratic life in the 18th century. The room's features include a carved and gilded ceiling, marble fireplace, an enormous glass chandelier, and velvety wall coverings with matching drapes.

The Dundas family and their friends depicted in their pomp, eavesdropped on educated judgments about another generation's artistic labours. In an adjoining room was a Brueghel, and elsewhere Gainsborough's portrait of George IV as Prince of Wales.

What would they have thought of early 21st century nudes, and pictures with titles like Dales Barns, Rockpooling at Tynemouth, Holiday Cottage Kitchen, Venice Dusk, and Memories of Ullapool? For more than 10 hours, Charlotte, Nina, Vince, and their colleagues working as temporary porters, fed a succession of paintings onto six easels for the judges' scrutiny and verdicts.

An attempt at Marilyn Monroe was entitled I Wanna Be Loved By You – "a plea from the heart. A good title to put before a judging panel," said one of its members.

A street scene earned a more favourable response. "That's the best set of railings I've seen all morning." But no. 627 was rejected. It was an abstract in acrylic and called Gordon Brown. Not good enough was the panel's decision.

Their chairman admitted their overall task had been "tricky." "It's a fascinating exercise. I'd describe the entries as a mixed bag containing a few nuggets," said Worthington. "There are some very committed artists out there, and you can't always distinguish between the professionals and amateurs. Some 'weekend' painters are extremely competent. They are good enough to produce art full-time but for whatever reason have taken a safer path through life.

"As a judge you are always trying to seek out the truth of an image. You can spot those who are copying a style. What we're always looking for is the true spirit of the artist, those seeking to express something of themselves.

"We may have to be harsh in our assessments, but that's why we're here – to offer an honest opinion based on experience. We haven't been unanimous on every decision. The response to a painting can be extremely personal. You might not like it, or want to hang it on your own wall, but it can still catch your eye and stimulate the imagination."

The public now has a chance to confirm or rubbish the judges' choice
of prize-winners from among those selected for the show. Visitors are
being asked to vote for their favourite three pieces.

The overall winner of The People's Choice will receive £2,000. They may be from Batley, Bingley or Barnard Castle, Harrogate or Hebden Bridge, Sheffield, Shipley, Sunderland, Thirsk, Wakefield or York.

The event, in part financed by a £10 entry fee for each work, marks the first major artistic venture at The Station, Richmond's former railway terminus, which has been redeveloped by a locally-based charity.

In its first few months it has invigorated the town socially and commercially. It has a cinema, small museum, restaurant and café, and niche businesses centred mainly on food and drink.

Now its cultural credentials are established, too. Donald Cline, a trustee of the project, is confident the "A1" can become one of the most significant open exhibitions in the country.

"The response was remarkable, the calibre of the judges gave it gravitas, and The Station is the ideal venue to showcase the region's artistic talent."

Back at Aske Hall, Mandy was anticipating more disruption. Hundreds of disappointed entrants have to retrieve their rejected work by July 11 – any time between 10 and noon. Some are ever-optimistic, whatever the critics say.

"Awful," was the consensus on one work. "Sale price £300 – insurance value £250" was its creator's response.

The A1 Open Summer Art Exhibition at the The Station, Richmond, is being held from July 14 until August 31.

The principal rooms and contents of Aske Hall can be viewed on September 11-12 as part of the Civic Trust's Heritage Open Day weekend. Admission free. 01748 822000, www.aske.co.uk