I had cause to study the lineage of the jujutsu taught by Jan de Jong recently.
Tsutsumi Hozan Ryu is supposedly the jujutsu taught by the Saito brothers who were Jan de Jong's original instructors.
Jan de Jong didn't start referring to THR until the mid 70s and every grading certificate of Jujutsu-kan and the Jan de Jong Self Defence School only refers to Tsutsumi Ryu, technically a completely different school to THR.
In 1999, Jan de Jong graded Peter Clarke 4th dan and referred to Jan de Jong Jujutsu for the first time on the certificate. Until his death all other certificates continued to refer to TR but those of the highest grades - Peter Clarke, Rob Hymus, Paul Connolly, and Greg Palmer - all referred to Jan de Jong Jujutsu.
After Jan de Jong's death, all the senior instructors went their own way.
Rob Hymus of Indian Ocean Dojo refers to THR. Hans de Jong of the Hans de Jong Self Defence School also refers to THR.
Peter Clarke of Southern Cross Bujutsu has a very good explanation of how he founded Jugo Tsutsumi Ryu on his website. Whether 'jugo' is actually translated as 'Australian' is a contentious issue according to various Japanese sources, however, it's saving grace is that it could be a clever rearrangement of 'goju' (hard-soft and referring to Goju Ryu karate) to 'jugo' (soft-hard) to emphasise the association with the philosophical construct that supposedly underlies jujutsu.
Greg Palmer also founded his own school and changed the name of the jujutsu he taught to Keikai Ryu which is supposed to translate to Gregory. Unfortunately the lineage of Jan de Jong to Greg Palmer and Keikai Ryu died with Greg. It may have died with him but it is not to be forgotten and forms part of the lineage that is the jujutsu taught by Jan de Jong.
Most interesting of all is the jujutsu taught by Jan de Jong Martial Arts and Fitness. The school's (not to be confused with school of thought or tradition) principal is Maggie de Jong with Paul Connolly being the 'seniour instructor' of the school. The JdJMAF website does not refer to a style of jujutsu by name but rather to the jujutsu taught by the school as being 'based' on THR. A no-name brand of jujutsu.
Pat Harringon in Principles of Jujitsu describes the lineage of Australian jujutsu. She has the successor of Jan de Jong and THR as being Graham Dunn. Graham was a devotee of Jan de Jong's teachings and his association with Jan de Jong influenced his teachings and his style of jujutsu, however, you'd need a dotted line at best to include his teachings with the lineage of the jujutsu that Jan de Jong taught. Harrington is guilty of poor research, a not uncommon feature of the martial arts literature.
What about Jan de Jong Jujutsu or Jan de Jong Ryu? It would appear it had it's moment in the sun for a twinkling of an eye. Even though Jan de Jong considered that he'd changed what he'd learnt so much that it was no longer THR, it would appear that THR possesses more currency than JdJR.