I believe Jaap to have been the most pivotal person in the New Zealand Kawaishi jiu jitsu lineage. He amalgamated the early 'jiu jitsu' of Maurice van Nieuwenhuizen, the Shin Nakada jiu jitsu of Johan van der Bruggen, Kawaishi judo and jiu jitsu as learnt under Jean de Herdt and Mikinosuke Kawaishi, and the Budokwai's jiu jitsu as learnt from Gunji Koizumi. Largely unknown in this country, he taught both Henk Fekkes and Hans van Ess, who separately brought jiu jitsu to NZ in the early 1960s. Today, two thirds of the jiu jitsu clubs in NZ trace their lineage back to these two pioneers, and therefore, Jaap.
The greatest of respect and deepest condolences.