Russian sourdough loaf

This turned out better than it looks in my picture. The crust is crunchy and not toothbreaking and the crumb is moist and tastes good (if you like wholemeal rye bread). I imagine the weakness is the slight sink in the top, and that seems to come from overproving - I think it was proved after 8 hours but gave it the recommended 16, and at that point, any draught can affect the bubbles - it had risen a lot in the tin.  Recipe is from Andrew Whitley, who was in the BBC sound department in Moscow in the sixties. It would be called Russian black bread or German grey bread (Graubrot) - possibly an acquired taste.