You know if it was emotional infidelity, that would explain their awkward body language and their terrible kisses and the off aim and target. Like >>495 said the MET dance off could have been a PR test to see how the public would respond to the two of them together.

I don't think they'd take such a risk for a one night stand. The one night stand could've been easily buried. The Sun probably had proof of their long standing infidelity. That would damage their images way more than a one night stand.