Imagine this: yesterday I had four 120 films to develop, two taken on Saturday during an unrepeatable trip to London. The other two were unimportant, and easily replicated test films. These were randomly loaded, two to a reel and the two reels put into a three reel Paterson tank. I used one litre of fluid to cover the two reels instead of one and a half litres that would have been required for three reels. Still with me? Unfortunately, as it transpired, I didn’t push the second reel all the way to the bottom of the centre support tube; the result is a sort of high tide mark all along the edge of two of the films. Can you guess which two films were ruined?