In the first quarter of the 20th century the company became one of the leading purveyors of fountain pens in England, upgrading its facilities numerous times to meet expanding demand. In 1909, Conway Stewart registered as a Limited Liability Company; and in 1919, moved to 31/32 Shoe Lane, London. In 1923 the thriving concern moved to 75/82 Shoe Lane, where it occupied six floors, and employed over 500 people. In 1935 Conway Stewart listed its shares on the London Stock Exchange, raising further capital for expansion and development.

Over the decades, Conway Stewart pens have been associated with many of the most famous people and events of British—and world—history. During the huge growth in letter writing during the First World War (1914 - 1918), the company’s pens played a significant part in those cherished missives that passed between soldiers at the front and loved ones at home. Conway Stewart pens were also used throughout World War II (1939 -1945), by British Prime Minister Winston Churchill, and other British statesmen and government officials. Indeed, though the factory was bombed and slightly damaged during the Blitz, and a significant portion of the facility converted to munitions manufacture, pens were still produced throughout the period in a limited range. The already legendary firm remained under ration control until the late 1940s, but in 1951 moved it’s factory to Mile End, London, 36/44 Copperfield Road, and the modern post war era of Conway Stewart began.

Conway Stewart has made many British pens of iconic status, introducing such timeless classics as the Dinkie "the smallest practical fountain pen ever made" (launched in 1922), and still being made in the same traditional way today .This was the world's first pen to be made in volume in coloured resin, and began a historical connection between Conway Stewart and the use of exciting vibrant colours, a part of the crafter’s heritage that continues to this day. Other major product developments included the introduction of Universal and Pixie pens in 1922, the Dandy pen in 1924, a name still used, and the Scribe and International pens in 1933. Also, first appearing in the 1920s, the Duro pen remains highly regarded for its classic profile and understated elegance; and, the No. 58 (1949) which was introduced as "the finest pen ever produced by Conway Stewart", was the first of the great post-war Conway Stewart fountain pens.

Other famous pieces include the Conway Stewart 100, introduced in 1954, and recently re-introduced to celebrate the company’s centenary year; and the beautiful flower pattern pen of 1955 (the Company's Golden Jubilee), known as the No 22 "Floral", which is today produced in solid gold and hand painted enamel. Another classic pattern, the Herringbone (in green, red and blue and the ultra-rare silver and even rarer gold) was introduced during the years 1957/58. The Cracked Ice, and Tigers Eye patterned pens, introduced in the 1950s, still excite everybody who sees one for the first time, and are eagerly sought by collectors around the world, who willingly pay hundreds of times the original cost to acquire them.

In the 1960's the Company continued to produce, however, the advent of the cheap "biro" and ballpoint pens, and mass production in lower cost countries, began to alter the market for quality fountain pens dramatically. The use of fountain pens, like mechanical watches, began to wane, a fashion that the quality conscious consumer of the 21st Century has now significantly reversed. However, at the time the trend had a devastating impact on traditional producers. As a result in 1975 the company stopped production. Nevertheless, the trademarks, designs, and archives were maintained intact, and interest in the company, its beautiful pens, and its history remained very high. Following, a significant investment in research and developement, a new era began with a focus on making pens for those who appreciate traditional craftsmanship, objects of timeless beauty and utility, and the pleasure of using a fine scrivening instrument. As well, for the growing number of pen fanciers and collectors around the world, who treasured the Conway Stewart name, and all that it stood for, as Britain's greatest pen maker, a new era for the revived venerable old design and crafting house was born.

In the 1990's, a new range of pens was launched. Made from solid gold, the Elite Collection showcased the work of English master craftsmen in various fields, including hand painting, enamelling, and engraving. These exquisite instruments, which can sell for $18,000 (£10,000) and more, continue Conway Stewart's tradition of excellence, and are fitting companions to the pens of earlier generations. Conway Stewart was also the first modern day pen maker to reintroduce, after significant research, the use of casein as a material for making pens. Casein, made from milk protein particles (confusingly known as nibs), is dyed and then laid down under high pressure to form slabs, from which the components are eventually formed. Each slab must be cured in preservative for five to six months before "weathering," for a further two months, before any parts can be made. This lengthy period rewards the eventual owner with a material that has warmth and lustre that cannot be achieved in any other material. To celebrate the life of Sir Winston Churchill, and his prolific interest in writing and literature, in 1996 the Churchill Collection was created.

To celebrate its Centenary in 2005, Conway Stewart has launched the new One Hundred Series in various handmade resins, and the stunning Silver Duro pens, which are made from pure English sterling, over-laid with resin veneer, echoing the great designs of the Edwardian era. Indeed today, Conway Stewart offers a range of 350 different pens, in 7 different styles, and over 50 colours, while the company continues to expand its scope and sales worldwide. Also in 2005, a Casein 100 Special Edition was issued, bringing one of the most durable and beautiful materials ever used to fashion a fine pen to a fresh, vibrant 21st century instrument.

Owners of modern Conway Stewarts are in excellent company, as Conway Stewart pens have always been the preferred choice of the most discerning and famous people from around the world and this tradition continues to this day. Her Majesty, Queen Elizabeth II, and The Duke of Edinburgh, were presented with two Conway Stewart pens from the Elite Collection, to commemorate their Golden Wedding Anniversary. Recently, Prime Minister Tony Blair presented Russian President, Putin a Conway Stewart Churchill Burgundy Fountain Pen, on a state visit to Russia. Likewise, French President, Jacques Chirac was given a Brown Marble Churchill to celebrate his 70th birthday. Conway Stewart was the official pen chosen by the British Government for the G8 Summit at which Prime Minister Blair presented a No 58 set to each of the G8 world leaders. Britain’s most revered pen crafter is supplier to No 10 Downing Street, the official residence of the British Prime Minister, as well as, the British Royal Palaces.

Both Presidents Bush and Clinton own Conway Stewarts. Many international celebrities, from the entertainment industry, to government houses; from industry, to science; also enjoy Conway Stewart pens. Rick Wakeman, rock star and pen enthusiast, has a large collection of Conway Stewart chirographic instruments, of which he is justifiably proud.

In 1905 when Conway Stewart was started, Jarvis and Garner had a single aim, to produce elegant, timelessly beautiful, yet functional writing instruments, today one hundred years later their vision and passion still live, producing beautiful and extraordinarily, finely engineered writing implements, making those original goals as fresh and inspiring as ever. Elevating the renowned élan connected to Conway Stewart by history and figures of the greatest stature, are special and limited editions such as the Centenary Overlay and Elegance, where scriveners of every sort will find luxury and inspiration in a single instrument.