Thank you all for your comments and thoughts. Some useful stuff.
This has got to be a classic example of what not to do.
Two things come to my mind: the ladder and the stabilisers.
From the safety videos I have watched, setting up a ladder on top of a tower is a huge NO. Here, the force the base of the ladder applies to the tower causes the top of the tower to be pushed away from the wall. The weight of the man up the ladder aggravates this.
There appears to be a stabiliser at the right base of the tower but it is aligned along the path. This plays no part in stopping the tower from tipping. Putting the stabiliser in the correct position would obstruct the road. This would mean speaking to the council beforehand, getting permission, sorting out bollards et c.
The tower is on a public pavement and there appears to be no provision for passers by. ( Luckily for me, my land extends around my house enough to put up a tower).
Those two guys were lucky to walk away from that one. At least they managed to land on their sides, which if you have to make a landing, is probably the least bad way to do it.
Any thoughts?