Good point, could be the issue.
However, the below works (in layout.phtml) as expected.
But if I remove the first line, error_get_last() does not find a similar deliberate error in my view.
echo $this_var_does_not_exist; // THIS WILL CAUSE AN ERROR
echo $this->layout()->content; // CONTENT FROM VIEW
$this->arr_error_get_last = error_get_last();
Thanks for your help, much appreciated.