Tertis (1876-1975) singlehandedly transformed the status of the viola as a musical instrument, rescuing it from its hitherto lowly reputation as the Cinderella of the orchestra, an instrument of refuge for "down and out" violinists. Tertis made it his mission to change this state of affairs. During his lifetime, composers as eminent as Ralph Vaughan Williams and Gustav Holst wrote pieces especially for the performer.

John Gilhooly OBE, Director of Wigmore Hall and Chairman of the Royal Philharmonic Society, unveiled the English Heritage Blue Plaque and said: "Tertis's legacy is profound and far outreaches the confines of viola playing, as it set a precedent for many other instruments and solo performers. It is a great honour to unveil this plaque in memory of an extraordinary man who stands in the company of Ysaÿe, Kreisler, Casals, Thibaud and Rubinstein as one of the greatest instrumentalists of his age."

Born in Hartlepool to Polish-Jewish immigrants, Tertis grew up in Spitalfields in the east end of London, "a place," he remembered "of such intensity and squalor that I wonder that I have lived to tell the tale." He left home at 13 and after a period as an itinerant pianist, he went to study at the Royal Academy of Music in 1895. It was there that Tertis took up the viola to help make up a string quartet. Tertis later wrote that, even on an old cut-down instrument, "I loved the timbre, I loved the quality from the moment I studied it, and from that time I worked at it myself, for the simple reason that there were no pedagogues for the viola."

By 1900, at the age of 26, the Royal Academy had appointed him to the newly created post of Professor of Viola. He played in chamber ensembles with many distinguished musicians, including the pianist Artur Rubenstein, who called Tertis "the greatest glory in England in the way of instrument or players." Beauty of tone and expressive intensity were Tertis's hallmarks: the word "passionate" often used to describe his playing.

Tertis's profile became increasingly international, and he commissioned a number of high profile composers to write new music for the viola including Ralph Vaughan Williams (Flos Campi, 1925) and Gustav Holst. Tertis initially rejected William Walton's Viola Concerto (1930) as too modernist, but came to hold it in high regard. To further augment the viola's hitherto limited repertoire, Tertis was also an indefatigable arranger of pieces written for other instruments, including Elgar's Cello Concerto, Mozart's Clarinet Concerto and Delius's Violin Sonata No.2.

In 1924, while in Paris, Tertis bought an uncommonly large Montagnana viola. Once refurbished, this became his instrument of choice, boasting a rich tone and volume, and was used on his many subsequent recordings for Columbia records.

Rheumatism caused Tertis increasing pain and he retired from performance in February 1937. Seeking other means to promote the viola, he began work on developing a new-specification instrument. The key feature of the 'Tertis model' was its size - it was 16 ¾ inches long, "the maximum length for playing under the chin", as Tertis explained - which meant for improved C-string sonority, or resonance on the lowest string. The design was widely adopted: over 600 Tertis models had been made in seventeen countries by the mid-1960s.

In 1961, Tertis and his second wife, the cellist Lillian Warmington, moved to Wimbledon and a ground floor flat in a large detached red-brick house at 42 Marryat Road - the building now marked with an English Heritage Blue Plaque. This was Tertis's retirement home, but for a man in his eighties and nineties he remained remarkably active. He continued to promote the 'Tertis model', and gave his last public performance in spring of 1964, at a meeting of the London Philharmonic Society club. Afterwards he continued to attend concerts, especially those by his friend Artur Rubinstein; Rubinstein's gift of a new hi-fi was delivered by Harrods to the Marryat Road flat in 1970, and greatly appreciated. Tertis died at the flat in early 1975. An obituary in The Times described his life's work as "the complete emancipation of the viola from its very humdrum occupation to the full rank of a solo instrument."

Margaret Lyons, Chairman of the Tertis Foundation and the current owner of Flat 1, 42 Marryat Road said: "Lillian Tertis, Lionel Tertis's widow, was absolutely determined that everything that could be done to preserve his memory and remember his heritage, was done, including setting up the Tertis Foundation in 2003. Sadly she died in 2009, so she did not know that we had gained an English Heritage Blue Plaque in his memory, but it is a wonderful recognition of his life and work and we are all completely thrilled to see the Plaque commemorating all that he did for the hitherto neglected instrument - the viola."

The English Heritage London Blue Plaques scheme is generously supported by David Pearl, the Blue Plaques Club, and members of the public.