Because of Brainin's Jewish origin, he was driven out of Vienna after Hitler's Anschluss of 1938, as were the violinist Siegmund Nissel and violist Peter Schidlof. Brainin and Schidlof met in a British internment camp. Like many Jewish refugees who came to the UK for safety, they became "aliens" and were kept in confinement.
Brainin was made free after a few months, but Schidlof stayed in the camp, where he met Nissel. Finally Schidlof and Nissel were freed, and the three of them were able to study with violin teacher Max Rostal, who taught them free of charge. It was through Rostal that they met cellist Martin Lovett, and in 1947 they formed the Brainin Quartet, which was renamed the Amadeus Quartet in 1948.
The Amadeus was one of the best-known quartets of the 20th Century, and its members were given many honours, including:
- The Order of the British Empire, presented by the Queen.
- Doctorates from the Universities of London, York, and Caracas.
- The highest of all German awards, the Grand Cross of Merit.
- The Austrian Cross of Honour for Arts and Sciences.
The quartet stopped playing together in 1987 after Schidlof died, because the others thought that no other violist would fit in to the group so well. Norbert Brainin continued to perform as a soloist, often performing with pianist Günter Ludwig.