It is indeed a clematis, one of the macropetala (think that's right) variety. They are early flowering and come in several shades. There are actually 2 plants in there, one either side of the arch. This one has a lovely creamy underskirt while the other, which is normally slightly later, is true blue. Have another pinky one in the front garden but not so prolific. In the last couple of years he was home, Fred used to go around with secateurs snipping off all the flowers when they started to bloom so it's a double pleasure to see them flowering now. Must admit I am a clematis (and orchid) fanatic so probably have too many in the garden of different varieties but several of them have buds ready to burst. Just hoping the forecast bad weather doesn't ruin the flowers. Hope you all have peaceful days. xx