The Highway Code has a special section on parking.
As well as the "shouldn't park facing traffic", one of those naive dreams from the times when there were only eight Austin Morris cars in the country, it lays down some places where you must not park
1. on double yellow lines.
2. a pedestrian crossing, including the area marked by the zig-zag lines
3. opposite or within 10 metres (32 feet) of a junction,
4. on the pavement
There's some other restrictions too: tramways, motorways, etc. It would be entertaining to run a competition in which you try try and break as many of these rules as possible in one go.
This car, P218WHW, was only parked here for less time than it took to get the post office across the road to issue some air mail stamps and write a receipt; 15 minutes or so. Perhaps this was the only short-stay parking in the area, with the normal short-stay options (pavement, double yellow lines) further up Cotham Hill being taken.