how to remove a file from repository and history?

[Jonas Stein]

I added some large binary files in the past.
That was a bad idea, as i recreate them often with my source files.

But i was quite new to hg. So i want to 
a) delete the binary files now from the repostitory as it consumes to much 
space in my quota
b) prevent hg to add them again. (i think .hgignore will work)

Any ideas for (a)? 

Thank you very much.

-- 
Jonas Stein <news at jonasstein.de>