No pic only description. What is this plant?
 

I know.... I am as much use as ________ fill in the blank.

Currently trying to identify a flowering shrub (seen also as tree).

The plant's bark is light grey and smooth with many branches.

The flowers themselves are a good 10-20cm and flower upright prior to leaves growing. The season appears to be April for a two week period.

The flowers are coloured white, but have stains of pink in them, and open out to around 15cm.

Sorry for the poor nature of this, but other than calling at the house or sneaking a clipping (oops) I am unsure how to progress forward.

regards