It all seems a bit odd to me. The relationship is supposed to have been carrying on for 10 years. I mean,
10 years? 
Do we take it Mrs Tarrant is blind, stupid, an ostrich, or what? If she's only just cottoned on, she must be at least one of these.
I think she's a drama queen and she's making sure she gets the sympathy vote in readiness for the alimony claim. It doesn't make Chris Tarrant any better, by any means, but I think there's more to the story than meets the eye.