There’s this weird British urban slang where they stick random ‘h’s in where they don’t belong in between ‘st’ sounds in words - shtreet, shtation, shtraight. And by urban I don’t mean black, I mean it’s a London/city thing. People don’t talk like that in the countryside .... It’s been going on for about 25/30 years…

Everyone knew Amber was bi before she married him, so I doubt it’s her.