This one is indoors with the sun coming through a window and falling onto a plain wall. I folded the hood back then just angled the camera until I saw the flare, took one picture then pulled the hood forward - flare gone.
This second example was taken outside. I did the same procedure as before.
The second pair of pictures have another area of flare that wasn't removed by the hood. It's not obvious so I've ringed it in the next picture.
I could also get the lens to produce some more obvious flare even with the hood in place so it's not a 100% solution, but hoods never are. But I think it's a worthwhile addition.
I also wanted to add a note to say that the lens I have is an MM type with a serial 72*****. There was, apparently, an earlier version of the 18mm which may behave completely differently.