David Messum wasn't born into a particularly arty family, but as art always inspired him, he left school at the age of 17 and wanted to work for an auction house. He recalls: "I went directly from school to Christie's where I had a meeting with Ivan Oswald Chance (Christie's chairman at that time) who said there were no vacancies in the office, but that he could give me a job as a porter. I worked under the head porter, Jim Taylor, who was a former sergeant major and an extraordinary character who became a good friend. I fell in love with the business. At the time I liked furniture as well as pictures which, of course, later became my speciality."

After a year as a porter, he was given a job at Christie's front counter, a good first experience in dealing with clients. He moved to Bonhams for a few years until a dealer mentioned that his company was vacating a gallery in Bourne End in Buckinghamshire, near where David lived in Marlow with great storage at the back for pictures and he took the opportunity to leave the auction world to become a dealer.

While Mark Weiss also went straight into the art world after school, he joined his parents in their gallery in Colchester in Essex, where they had started dealing in the early 1960's handling paintings from the 16th to the 19th century, including the local East Anglia School. Mark explains: "My parents were both trained artists, and my father hitherto had been an art teacher in a local secondary modern school. Initially dealing from home, they quickly became incredibly successful, and by the time I joined the family business, which was simply called Ivor and Joan Weiss, together they ran a large dedicated art gallery. Above the gallery was a frame workshop employing six staff, as well as a restoration studio run by my mother who had become our principal restorer and employing three other restorers. My father also had a full timer secretary and PA. So it was quite a large operation, and far bigger than anything I have ever had since!"

Paul Mitchell on the other hand was born into a long-established London art dealer family. His father set up John Mitchell Fine Art in 1931 and Paul worked in his father's studio and art gallery, where he trained in picture conservation for six years during degrees in art history and architecture. During this time he found that "... trying different styles of frames on artworks was fascinating. Recognising the potential for this barely researched subject - so influential in selling - I began augmenting our frame inventory and set up my own business in the mid 70's."

Looking back on such a successful career in the art world, we asked them what they see as their greatest achievements and Paul says: "Over the last few decades, it has been a joy to have helped persuade viewers to look beyond an artwork to assess its frame and how it influences perception of the subject. Is it the genuine original, contemporary to the period, later or earlier, another nationality, or simply a poor reproduction, a mass-produced pastiche...?"

Paul has researched, co-authored and published two major works on the history of frames and this could have only been possible through accumulating their unrivalled Photographic Frame Archive in order to classify the countless styles of European frames by nationality, chronologically. Through lectures, publications and institutional appreciation of frames Paul and his son Mark continue to open eyes to the beauty and quality of fine frames and their aesthetic impact.

For David Messum it was undoubtedly the fact that he felt that the whole field of British Impressionism seemed a bit untapped, "...so I published my first book on the subject in 1985 with Laura Wortley (the then archivist at Messum's). It was really the first major text on the subject and was well received despite, when it came out, some critics saying the subject was an oxymoron. However, nowadays the term 'British Impressionism' is widely accepted and there are even rooms at Tate Britain devoted to it."

Out of this first publication grew the publishing arm of Messum's which is now an important part of their operations. Along with the specialist libraries, Studio Publications is based at the Lord's Wood's studio, where they undertake much of the research into artworks as well as the numerous Artists Estates that they have come to represent.

Mark Weiss sums up his achievements when he says: "Allied to the long career I have forged, through the very specialist knowledge I have acquired over the last fifty years, I am most proud of the discoveries that I have made, and great paintings that I have handled; works which now grace famous museums and institutions around the world, as well as assisting great clients assemble notable private collections. I am also of course very proud of my incredibly beautiful gallery in Jermyn Street."

And of course discoveries make this such an exciting business. Mark has been fortunate to look back on many of them, but some of the real highlights that immediately come to mind "....are two by Van Dyck, one of Pompone de Bellievre, the French Ambassador to London. This now hangs in the Seattle Art Museum.  The other was St. Sebastian prepared for Martyrdom, a painting which had been removed and then lost from the Escorial in the early 1800's and which was bought back by the Spanish government and rehung in the exact spot that it formerly hung.  More recently we handled a wonderful newly discovered painting by Bartholomeus Spranger, the Flemish mannerist artist, which had been commissioned by the great collector King Rudolph II, for his palace in Prague. Today it proudly hangs in the Berlin Gemäldegalerie."

For Paul Mitchell many frames have proved to be exciting discoveries over the years with some finding their ideal partner sooner than others. Key examples are a Florentine parcel gilt walnut 16th century frame which proved to be the original for Fra Bartolomeo's Rest on the Flight which is at The J.Paul Getty Museum, Los Angeles. In London, you can see a Bolognese 17th century cassetta frame, the exact contemporary pattern for Guercino, The Dead Christ mourned by Two Angels, at the National Gallery and the finest reeded 'Degas' pattern frame, acquired by The Art Institute of Chicago for The Millinery Shop, surely one of the artist's greatest works, also stands out as one of those perfect matches.

David Messum really helped rediscover British Impressionists. He says: "From my early days as a dealer, I was always drawn to these painterly plein air pictures. I've always liked realist paintings, especially ones with humble subjects that enshrine outdoor life. That's what got me interested in Newlyn pictures in the early 1970's. These artists broke away from the traditional ideas and techniques of Royal Academy stalwarts and painted more realistic, earthy subjects including the daily toil of ordinary men and women. I think the light is also key to these pictures - that's really the reason that they set up these artist colonies in the Southwest in the first place. This is why I titled my first British Impressionist exhibition 'A Breath of Fresh Air' - I still feel that's the attraction for me."

David soon started representing artists' estates and the gallery now represents around 20. "One of the biggest and most extraordinary is that of Wilfrid Gabriel de Glehn (1870-1951), which was initially valued for probate at £100,000 shortly before we took it on. Over the three decades we have represented the estate, sales have exceeded £20m."

With decades in the British art world, the dealers have of course seen dramatic changes, both positive and negative ones.

In the world of frames that has meant that the huge advances over some thirty years in frame studies have elevated the subject to the scholarly status it deserves alongside the fine and decorative arts. Witnessed by museum exhibitions in Europe and North America all of which showed far greater public interest than expected. In 1996 the National Portrait Gallery held the first frame exhibition seen in the UK (sponsored by Paul Mitchell), with a ground-breaking catalogue. Paul adds: "The Frame Blog produced by Lynn Roberts is the most remarkable encyclopaedic resource of frame studies, an unrivalled global focus on the subject. Personally, I am pleased that after many years of encouragement, leading auctioneers now illustrate artworks WITH their frames."

Mark Weiss sums it up when he says "Without doubt the greatest changes have resulted from technology; mobile phones, the internet and the development in art science have impacted the art world enormously.  In the early years of my career, if you went to a small country auction and saw something exciting, unless a competitor had viewed the sale you could buy the painting without any competition. Today because of the internet, it gets bids from around the world. The other most significant changes are in taste, with the contemporary market becoming ever more in demand, and of course in supply, with fewer and fewer fine Old Masters available in the market."

A summary David Messum certainly agrees with: "The salerooms are much more powerful now. They are effectively marketeers who buy and sell rather than act solely as traditional auctioneers working for the vendor. In terms of demand, the 19th century picture market seems to have softened somewhat and many fine paintings from this period are not expensive today. Over my time, I've noticed how certain markets shoot up quickly whilst others seem to fall away just as quickly. Impressionism though seems to be never out of fashion."