On a happier note...
I had a lovely day digging yesterday. A few heavy showers in the morning, but most of the day oK, quite warm at times and nice and sheltered down in the room we're excavating. Early in the day the detectorist found a really nice coin on the spoil heap. I was so pleased for him - I still felt guilty about the one I found. We had a good look at it and I more or less identified it (not that everyone would believe me) - I actually confirmed it today in the library (Valens, 4th century, minted in Arles).
In the afternoon, I was busy clearing out backfill from a trench that had been dug last season, when what did I find but another one! Almost identical but more worn, so I haven't been able to confirm that one. I have now found 1/6 of the coins from the entire site and 1/3 of the ones from this building!
One of the other trenches now has quite a sizeable chunk of painted wall plaster exposed. It was supposed to be an outside wall. Evidently not.