The memorial plaque in Willow Road was part of a scheme by the Association of Jewish Refugees to commemorate prominent emigres

Friends and family of Milein Cosman and Hans Keller gathered at their former Hampstead home to unveil a memorial plaque.

The event was organised by the Association of Jewish Refugees as part of a scheme to commemorate prominent emigres who fled to Britain from Nazi Europe.

Cosman, who died in 2017 aged 96, sketched some of the 20th century's greatest artists and musicians, inculding Benjamin Britten, Yehudi Menuhin, Wilhelm Furtwängler, Thomas Beecham, TS Eliot, Francis Bacon, Barbara Hepworth and Henry Moore.

She often collaborated with her Viennese husband, musician and BBC broadcaster Hans Keller, including on a book on Stravinsky.

Cosman liked to sketch swiftly in ink and pencil, capturing figures in motion, creative people in the act of creating.

"It's nice when people are not aware of being sketched," she told the Ham&High in 2008. "They are just themselves. I am at my best when I am working very fast."

Born Emilie Cosmann in 1921 in the small German town of Gotha, she was educated in Dusseldorf then Geneva, and came to Britain in 1939 following her brother who was already in Scotland.

She trained at The Slade during the war when the art school was evacuated to Oxford, and studied drawing under Randolph Schwabe and lithography with Harold Jones. In her holidays, she would visit her mother's flat in Belsize Park Gardens where they "slept in a little larder on ledges" and from where she ventured forth to nearby Belsize Park tube station to sketch people sheltering from the Blitz.

At Oxford she met Iris Murdoch, then a student and drew her portrait, commenting on the sharp features in the baby face, and the acute intelligence. It was Milein's first lithograph and showed her ability to get under the skin of her subjects. After the war, she moved to London, taking rooms in Aberdare Gardens, Adelaide Road then Christchurch Hill, and began freelancing as an illustrator, submitting sketches to magazines and newspapers. She became a regular contributor to the Radio Times, supplying portraits of interviewees.

She met Keller in 1947 and it was his face that first drew her attention. She told the Ham&High "My first thought was, 'I wish I could draw him. He wasn't difficult to capture and, in the end, I had a lifelong opportunity to draw him. I still went on after he died."

Born in Vienna in 1919 Hans emigrated to London after the Aschluss in 1938 and made his name as a music writer and broadcaster. He died in 1985 but in 2006 Milein established the Cosman Keller Art and Music Trust. It bequeathed her drawings and prints to the Royal College of Music in London. Her work is also on show at Wigmore Hall and held by the V&A and National Portrait Gallery.

The Willow Road memorial at the home of human rights lawyers Philippe Sands and Natalia Schiffrin was attended by the couple's niece Ena Blyth, His Excellency the Austrian Ambassador Michael Zimmermann, and Head of the Cultural section at the German embassy Dr. Ralf Teepe. The couple lived there from 1955-1967 when they moved to Frognal Gardens.

Although in later years Milein suffered from poor eyesight she took her sketchbook with her on her trips around Hampstead until well into her 80s.

"I feel like an orphan without it," she told the Ham&High. "Drawing for me is a tick, a kind of obsession. I remember when I was at school, and just six years old, the thrill of dipping your pen in the ink and making a mark on the page."

She added: "I am interested in people. I have always had an enormous number of friends. I like catching life on the wing - perhaps it is because of something restless in me."