I wouldn't be surprised if it wasn't Harry pushing this from the start, rather than MM: you can imagine how fast this type of thing spirals out of your control when you're married to a man with deep pockets, no real understanding of the law, and An Agenda.
'Oh no, this is so mean of the Mail!'
'It's fucking outrageous, babe, we'll sue!"
'But it'll be expensive...'
'I don't care! You are my family!'
'But, um, now I think about it, I suppose I might have mentioned a teeny thing to Serena...'
'Doesn't matter, we'll hang the bastards out to dry!'
'But, H, I'm not totally sure I didn't, um, ask Amal about the spelling of 'disingenous' before I sent it, which might look bad...'
'Doesn't matter, we're going to get those bottom-feeders!'
'But H...'
'NONE OF THIS MATTERS WE ARE TOTALLY IN THE RIGHT AND THEY ARE GOING DOWN THIS TIME HELLO, IS THAT SCHILLINGS?'
'Oh... fuck.'