How do I get rid of /var/lib/mysql/debian-relay-bin.###### files?

["Robert S" <robert.spam.me.senseless@gmail.com>]

I'm running a very simple mysql setup on Etch with no replication.  My
/var/log/mysql directory has become full of debian-relay-bin.######
files.  How can I get rid of these and stop them from filling up my
hd?

Here's my current config (which hasn't made any difference) NB I
haven't changed the contents of /etc/mysql/my.cnf:

# cat /etc/mysql/conf.d/CUSTOM.cnf
[mysqld]
expire_logs_days     = 2
relay_log = 'debian-relay-bin'
max-relay-log-size   = 10M
relay-log-space-limit   = 30M

I've tried the following with no success:

# mysqladmin flush-logs
mysql> PURGE MASTER LOGS BEFORE NOW();