Visual Tree Assessment Oak with Large split.

[jfc]

Doesn't look suitable for cable bracing, too low and easy for people to mess with the cables imo. But happy for more knowledgeable folk to disagree with that.
J.

[Khriss]

Cable bracing would be good if it were further  off ground, but fence off at collapse point possibly planting a couple or three trees there to further guide away walkers, so if it collapses it can be left. K

[Mazzoo]

1 minute ago, Khriss said:

Cable bracing would be good if it were further  off ground, but fence off at collapse point possibly planting a couple or three trees there to further guide away walkers, so if it collapses it can be left. K

I like that approach because it would be great for creating a habitat for saproxylic insects, could be a good justification for my conclusion.

[Khriss]

Yer,  always  think planting trees is a good idea 😉 i just must like trees or summat 🤔 K

[Dan Maynard]

Could it have happened the other way round though, split first and then that large branch taken off to reduce weight? In other words the mitigation has already taken place so just monitor, and the crack looks old and stable to me.

If everyone who looks at it recommends taking a bit off (to be sure) there will be nothing left after a while. That's what I always think about reducing end weight to reduce risk of failure, when do you stop?

I'm inclined to agree removing that whole side will just cause decline or toppling of the other side so it's either do nothing, reduce end weight, or fell the whole thing as a potential danger.

This one's above my pay grade though, in practice I'd look at that and recommend they get someone more qualified (and insured) to look at it.