After four years of widely varied roles in three-weekly repertory in Lancashire, where he also made the acquaintance of Brian Epstein, he returned to London, where he earned a high reputation in both BBC and ITV television productions (when all transmissions were live), films and theatre.
He was invited by John Neville, then artistic director of the Nottingham Playhouse, to tour West Africa for the British Council, along with a company including Judi Dench, who played Viola in Twelfth Night to Knapp's Feste.
The company performed in Nigeria, Ghana and Sierra Leone for three months, after which Knapp found an opportunity to travel in Africa and Europe, where at Easter he had an audience with Pope John XXIII in Rome.
Later in that year, sponsored by Olivier, he received a Churchill Fellowship in the Performance Arts of Japan and was off to Tokyo for nine months, with a Berlitz crash course in Japanese and generous introductions to star actors, choreographers and scholars for the study of Kabuki, Noh and, in particular, with the legendary "Charlie Chaplin" of Kyogen, Nomura Manzo.
He was to return to Japan many times over the next twenty-five years to direct a score of Japanese language productions, mostly of Shakespeare, often in partnership with Yamazaki Tsutomu, and where he introduced to Tokyo audiences, in a trio of roles, Watanabe Ken.
In 1970, he was invited by Ernst to go to Hawaii as a Visiting Professor to create a Performance and Production program, focusing particularly on the plays of Shakespeare and other European "classical" playwrights, as well as distinguished American authors.
He adapted Gounoud's Faust for young audiences and was performer/narrator in Verdi's Otello with the Hawai’i Opera Theatre He appeared at the Kennedy Center in Washington, D.C., in the role of Abbot Seigen in The Scarlet Princess of Edo by Namboku IV and Dr. James Brandon.
Knapp appeared with the Honolulu Symphony as narrator and recitalist for such productions as Schumann's Manfred, Honegger's Joan at the Stake, Schoenberg's Survivor from Warsaw, Prokofiev's Peter and the Wolf and many Shakespeare-inspired compositions by Mendelssohn, Tchaikovsky and others.