“....the relationship – even its duration – other than that they are middle-aged figures.”
A middle-aged British love affair - terrifying images of Hyacinth Bucket and the Major come to mind. An affair consumated with scones, & tea from her Royal Doulton china with the hand painted periwinkles.
Actually, Major had an affair with Edwina Curry, Still fits the intent of your comment though, was only revealed in 2007, 20 years after.