UK laws:
The Pedal Bicycles (Safety) Regulations 2010
German laws:
https://www.gesetze-im-internet.de/stvzo_2012/
In short, both countries have two-brake requirements and reflectors. The German law requires lights (white/red) with certain specifications (dynamos of certain wattage, etc...)
The HANDS employed for brakes for front/rear are reversed between the UK/Germany and the fault would automatically pass to the cyclist.
Interesting times.