I had thought it was a pocket handkerchief tree, Davidia involucrata. But now, looking at Desert to Jungle's post and photos (13th May), I realise it is not. It has similar 'falling handkerchief' like blooms with a red centre, but cup shaped petals rather than two bracts and a green stigma within the red centre.
We inherited it with the house and it grows in the most sheltered south-facing corner of our walled garden. It doesn't look like it will grow into anything like the size of the Davidia involucrata. But it is lovely!