I fly between Germany and UK pretty frequently, and whilst the UK doesn't check the passport on the way out, Germany do check it on the way out (you get checked

I fly between Germany and UK pretty frequently, and whilst the UK doesn't check the passport on the way out, Germany do check it on the way out (you get checked again when entering into UK). I have heard of friends of friends who overstayed a visa and get found out on the exit gate (usually bringing a lawyer/embassy official to talk through things). This can lead to a (temporary?) travel ban to Germany and a fine.