Despite the conventional red/blue (left/right) spots on the shower tap, a clue suggests otherwise. . . the danger warning for very hot water is on the right hand side.
Sure enough, cold water comes out of the left spout and blessed hot, from the right.
This time I managed not to flood the floor until it came through the ceiling below.
In Golub Dobzyn 2 and a half years ago, it took time for the confusion to clear, so it was a very different matter!