Among the conductors making guest appearances in the early post-war period were Walter, Furtwängler, Victor de Sabata and Sergiu Celibidache. Such starry events were the exception; as a rule the orchestra worked with less eminent conductors, giving an unprecedented number of performances. In 1949–50 they gave 248 concerts, compared with 103 by the London Symphony Orchestra and 32 each by the Philharmonia Orchestra and RPO. After a seven-year interregnum the orchestra engaged a new principal conductor, Eduard van Beinum, in 1947. He was initially able to work with the orchestra for only six months of the year, because of restrictions on work permits for foreign nationals. Guest conductors stood in during his absences. In 1947 the London Philharmonic Choir was founded as the chorus for the LPO.