QFT, there not polar opposites, and if you have that inate understanding of grips/ arm control, balance, timing and pressure, and endgame tactics then one should be able to do both, there are differences, but thats what makes life interesting,
Clark did have experience of something like traditional jujitsu: he was a student at Liverpool's Alpha Jujitsu Institute which was set up by Jack Brittain who got his black belt under Yukio Tani one of the jujitsu pioneers E W Barton Wright brought to the UK back at beginning of the 20th century. Although it seems that Clark learnt some stuff them high tailed it over to James Blundell's BJJA, which became the WJJF (sort of). Apparently Clark kept some Alpha Institute posters that he shouldn't have and displayed them in his dojo. Anyway, the WJJF syllabus is not, strictly speaking, jujitsu in the koryu sense. It's more dirty judo with some Karate, Aikido, catch wrestling and WWII combatives thrown in. Eugene McFadden
The "Gentle Art" .... Dirty Judo !!!! I get accused of doing that all the time !!! Headbutts, gauges, stomps all thrown in with a throw finishing the opponent ... The way forward !! Smurf