Lilley said with a crack such as this one, the tree can no longer be saved and the next focus was to get it down on the ground safely.
"The wider crew was on-site from around 4pm Sunday, with the site coned off, safely excluding the public from the area.
"The tree was felled in three sections, relative to the cracks within it. By evening the tree was completely down and the crew was working on laying it all flat to make it safe to be left overnight."
Lilley said all trees are inspected every three years, with this oak tree last being inspected in April 2019.
"While there were come conjoined limbs higher in the crown, a typical form issues that a tree of its size and age is likely to have, there were no significant defects noted at that time.
"The crack was very recent and we are very grateful that this was brought to our attention. This tree would have failed if it hadn't been felled.
Lilley said immediate hazards like this need to be reported to the Council as soon as possible by calling 06 349 0001 rather than posting to social media, which can be easily missed.
Whanganui District Council will look to replace the tree next winter.