[Exim] default delivery from aliases file

Various bits of on-line documentation led me to believe that I can put
a line like "*: edmund" in /etc/aliases to get all otherwise
undelivered mail sent to me, but it doesn't work, even when I added
the '*' in exim.conf:

system_aliases:
driver = aliasfile
file_transport = address_file
pipe_transport = address_pipe
file = /etc/aliases
search_type = lsearch*

What's the best way of achieving this?

Edmund