I don’t have lots to say here as I am still quite saddened. But today I had the terrible news that all Red-cap chicks in the box have gone - most probably taken by Ravens. We had some very strong easterly winds over the last few days, and my mum noticed the lid of the nest box was open. She had also seen ravens hanging around the box a lot (I was away in the field), so it seems these are likely to be the guilty predators. Ravens are very smart birds and it wouldn’t surprise me if they worked out how to open the lid.
I have taken the box down for repairs and plan on installing a catch to prevent this from happening again.