Krav maga has grown from being a secret martial art of one of the world's most exclusive elite forces into a martial art open to us all. There are now many excellent krav maga teachers in London and which ever part of the city you live you should be able to find classes nearby.
Krav maga is a very modern martial art and is very different from the traditional arts like aikido, judo and karate. It is a raw form of self protection based around real attacks including knives, axes and guns. It's a highly effective fighting method for street self defence.
A reasonable level of fitness is required but don't worry about this too much as this is something you can develop if you are willing to devote some time and of course effort to classes.
There are many options for learning krav maga in London and a little local research will help you to find a suitable venue. I would suggest you go along and watch a couple of lessons and talk to the instructors and teachers. What is it you want to achieve from learning self defence techniques ? Is it to improve fitness, to lose weight or to actually learn to defend yourself in violent encounters? Whatever your personal goals I'm sure krav maga will have a lot to offer and you will see great benefits.
