Green’s Dictionary of Slang

all in order, everything as it should be.

1886–96		Marshall ‘Une Affaire d’Honneur’ in Pomes 110: And the start was all Sir Garnet, Jenny went for Emma’s Barnet [F&H].
1912		E. Pugh Harry The Cockney 163: ‘Is there anything I can do, dad?’ [...] ‘No, ’Arry-boy. That’s all Sir Garny.’.
1932		‘P.P.’ Rhy. Sl. 5: All right this morning ’Oats?’ ‘Yus, all “Sir Garnet”.’.