His agent and itv wouldn't drop him like a stone for just having an affair with someone over the age of consent.
Considering that all the This Morning presenters are encouraged to adopt a “holier than you” viewpoint when interviewing anyone (which itself is always a bit Daily Mail-ish unless a presenter transcends that by having the charisma and general “good person” vibes of an Alison Hammond)… then an extra-marital affair would itself be reason to quietly remove someone (or equally something that would be quietly smoothed over by the show and never reported to us).
It would not be reason for a “close friend” to engage a full-on PR attack implying that she has discovered something she never knew before and can no longer work with him due to the “betrayal”.
That ceases being his own messy private life and becomes something that, if she knew about it, or is perceived to have known about it and not spoken up… it would kill her career by association.
The latter seems to be what we’re witnessing.