“austere with himself” - suggests that he didn’t indulge in his pleasures
“drank gin” - in order not to indulge in nicer things (wines) - although this is ironic as gin is much more alcoholic
“hadn’t crossed the doors of one in twenty years” "- “enjoyed” the theatre but did not indulge
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“But he had an approved tolerance for others; sometimes wondering, **almost with envy**, at the high pressure of spirits involved in their misdeeds”
* he would “envy” those who completed crimes and indulged in desires as he spent his life living morally and piously, repressing his innermost desires
* hyde may be a construct conveying the effects of repressing desires