Pied Great Tit; Carbonero Común Blanco

This unusually plumaged bird was feeding in the trees outside my window this morning. In spite of the Common name I have given it, it is just a Great Tit with most of the yellow missing for some reason. On the 1st picture (but the last taken) there is just a hint of yellow behind the throat, on the others there is a hint of olive near the collar of the mantle. Unfortunately the bird did not give a full frontal view in the open. I did get one photo of it in the depth of a tree with just the tail and a bit of belly showing.