@bplus Thanks for your kind, as ever, comments. Thanks also for finding another error! As you know I am normally very slow but I was in a hurry to win @STxAxTIC 's prize of an all-expenses-paid trip to the Great Pyramid of Giza, and it is something of a pity that here in lock-down the prize has been downgraded to a trip to my back garden. I shall at any rate enjoy weeding my strawberry patch and pruning my peach tree.
Perfect combo ...@FellippeHeitor Like bplus, you are too kind. This was only a little demo of my solution to STxAxTIC's problem. I was going to enquire about the sometimes-ragged line drawing. I shall know for next time.