Redirecting when merging two blogs into one

I’ve got a multisite installation where I want to merge two blogs into one, that is – current setup

example.com <- Main blog
example.com/ablog
example.com/bblog

I now want to merge the content of ablog and bblog into ablog so I get

example.com <- Main blog
example.com/ablog

The actual moving isn’t a problem and I don’t care that links to bblog won’t be correct anymore. But I would like to redirect bblog to ablog, for example a call to

example.com/bblog/x/y/lksdjal

would instead call

example.com/ablog

(redirecting to example.com/ablog/x/y/lksdjal is also OK). What is the best way of doing this?