I know a West-End production manager who, as a young stagehand, had worked on one of the revival productions of The King and I (I think it would have been at the London Palladium in the early 70's). According to him, and others I have heard in the business, Brynner was utterly loathed: demanding, aggressive, sexually bullying and insanely protective of an equally unlikeable offspring (to the point of laying hands on anyone who stood up to the boy) .
On his final performance the barefooted Brynner had to shuffle from the stage to his dressing room - the stagehands had, allegedly, tin-tacked the entire backstage area as a little gesture of their regard for the man.
It sounds like an apocryphal story - and possibly it is - but one thing I suspect many outsiders are blissfully unaware of is that the backstage working life of West End theatres was, up until relatively recently, heavily populated by members of old-school crime families and their acquaintances, who were all perfectly capable of exacting their own brand of retribution. (I met some very 'interesting' people - including, supposedly, the late 60's most successful cat burglar, as he described himself with obvious pride: ...never 'urt no-one - just climbed over the rooves of 'ooever was in the papers that week and nicked their sparklers....made myself a coffee in Mick Jagger's flat while 'e was snoring on the sofa in fackin' ladies underwear. Only caught me 'cause I fell off a roof in Regents Park and landed on an ambulance.)