![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEicuriYogFDh8uAhJgSaqmXrUJOLHCkoNZwFN2rCOudnpQ_Q-RSmJpYTWhsdn6I8dx6XYrl848fZxzsOIK-bPaNzPwHgJPlj68ODqxFaSsaYLbh79YP6QAkGnc9qrGjVCyX9Gll0fbhaAJH/s320/Observation+tower,Alderney.jpg)
I also dipped into "Festung Alderney" by Trevor Davenport and compared the diagrams to the actual sites I visited when at times the visibility was down to shrouded-under-a-white-cloth distance - not like the sky in this postcard. The book is pretty comprehensive, if rather niche.