Earlier this month, a police force posted a picture online of an aftermarket sat-nav on a car’s dashboard.

It nestled discreetly in the bottom right corner of the windscreen, alongside a police instruction that placing it anywhere else was ‘illegal’.

I forget which police force it was because the tweet has since been deleted. It wasn’t true, you see. The Highway Code and the laws that back it up give no particular location for placing sat-navs, beyond advising that ‘windscreens and windows MUST be kept clean and free from obstructions’, and that ‘glass or other transparent material shall be maintained... [so as to] not obscure the vision of the driver’.

Follow the very letter of the law, then, and you can no more place a sat-nav in the bottom right corner of your windscreen than you can anywhere else.