April 9th – Hiding in plain sight on the treeline of a small copse on Sandhills, near Shire Oak, is a Tetra mast. Painted matt brown to blend in with the background, it’s not a mobile phone cell tower, but one of the nodes of the emergency services radio communications and telemetry network for the UK.

Erected in the last decade, Tetra is a secure system designed for use specifically with emergency services in mind. Working at a lower frequency than normal mobile GSM, it’s more efficient structurally, provides secure, encrypted communications and provides all the features required for modern operations.

The network wasn’t without controversy, as the earliest systems interfered with TV transmissions in some instances, and it has proven very expensive to implement, although the system is in use now in much of the developed world.

There are a fair few of these installations around. Look out for them – like this one, they can be hard to spot, but mostly share the same, three-element design.