Mystery Magnolia

There is a tree tucked in amongst other trees in a corner of our garden. At this time of the year there are numbers of white flowers in bloom on the tree. They look like magnolias... but a variety not known to me. I would be so pleased if someone can identify the variety for me.
We had a good downfall of rain this early this morning. It was very welcome as the garden was becoming quite dry. Ironic really as parts of the North Island have had more than enough rain with flooding and power cuts.