Just pure salary comparison isn't enough though. London has crazy living costs, and Berlin's response is the heavy taxation (about 40%-45% including the compulsory health insurance).
(Against all rumors, Germany doesn’t have universal nationalized healthcare)
You can also choose private insurance if your income is high enough, which can then be cheaper for you than the mentioned 15%. The income limit for that is something like 55-60k/year, if I recall correctly.