Paul Mc Cann wrote:

It strikes me that if you cut through the first one it can only fall the
one way given that the others are in the way. That should give a little
elbow room to cope with the remaining trunks.

I suspect they're quite thoroughly entwined, so the cut trunk will
just hang there.

Well then you could just cut off 12" at the bottom which would allow
some scope to notch one of the remainder.

At the very least this action would have the same effect as notching on
this side. (i.e.) pre-dispose the others to fall in that direction

Notching does two things:-

It will tend to help make the tree fall in the desired direction.

It allows one to cut from the other side so that a 'hinge' is
formed which will allow the tree to be dropped accurately.

While cutting right through the first trunk will tend to have the same
effect as the first of the above points it won't do the second at all.
Since I would like to drop this tree quite accurately (to avoid
damaging trees we want to keep) the 'hinge' is quite important.

--
Chris Green