Tensions between Theresa May and Philip Hammond
The path of true harmony between Number 10 and Number 11 rarely did run smooth.
Remember, George Osborne and David Cameron were the exceptions, not the rule.
So we shouldn't be too surprised that there is friction between the occupants of those two addresses under the May government.
The PM and Philip Hammond have known each other for a long time and while hardly best friends, Theresa May clearly had significant faith in him to make him her chancellor not that long ago.
But before and after his giant U-turn over plans to increase National Insurance there have been tensions, and more reported in recent days as we approach tomorrow's Conservative manifesto.
This morning the chancellor's admission that he sometimes swears, as he sought to play down reports of rows with Team May, won't have helped.
Nor will the PM twice refusing to say he would still be her chancellor if she is elected.
She did, at the third time of asking give him her endorsement.
And moving him after the election if the Tories win would be a dramatic and risky move.
But this morning's excursion won't have helped relations between the two addresses.