Enjoying a good relationship? First Lady's reticent at first — I wasn't expecting that … (4,1,5)

I believe the answer is:

well i never

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(Other definitions for well i never that I've seen before include "that comes as a great shock" , "The call of the malingerer" , "That surprises me!" , "That's hard to believe!" , "Fancy that" .)

I've seen this clue in The Guardian.

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