Samurai Sudoku

I can while away many an hour on these logic puzzles, but was surprised to learn that they were invented by Howard Garns, an American, in Indianapolis in 1979. They are immensely popular in Japan, however, where the term Su Doku means ‘the numbers must remain single’.
Thanks to lockdown, I’ve become quite adept at the Super Difficult version, but always do them in pencil with an eraser handy!