Oh dear, Emma. What would Nanny think?

Emma Thompson is gradually acquiring the status of a national treasure but it's an awkward process, with two steps forward and one step back, writes Peter Rhodes.

She deserves to be heard on the subject of teenage language with all its grunting and y'knows and, well, like, innit.

Sadly, this crusader for better English spoiled things just a tad by telling a group of schoolgirls that if they spoke badly "you're going to sound like a knob."

Oh, dear. What would Nanny McPhee make of that?