Much of this developed from Mrs Thatcher's elocution lessons when she was aspiring to be PM. She never lost her lower middle class vowels, just dropped her voice a few tones. Iss-yu, involved with a long o and so on.
I used to know someone who always talked about Christ-mas, emphasising the T.
Schedule or skedule? Controversy on con-tro (stress) - versy? For (stress) mid-able or for-mid (stress-) -able?
As long as people understand what I say it doesn't matter too much, but that ultra-careful pronunciation (have you got a tiss-yew?) gets up my nose too, Gk.
This was going to go into Room 101 then I thought, best ask first. I often wonder when the pronunciation of ishoo became is-yoo. Same with appre-cee-iate. When I was at school it was ishoo with a 'sh' (so we must have been taught that). Then I went through a phase (a very short one) where I thought I was mispronouncing, and tried very hard to get my tongue around carefully saying e.h. Christ-i-an. Now I've gone back to saying Chrischan. So now when I'm in meetings and people say is-yoo, I purposely put a big fat ish in mine when I reply.