[Mailman-Users] how to remove badly formed email address from list

[Rachel Willmer]

I've got a user on one of my lists who's subscribed himself with the email 
address with a form of "myname at home"@isp.co.uk.

Of course, this address is completely undeliverable, and every mail out to 
the list bounces. So I'd like to remove this guy. But I can't figure out 
how!

If I deselect him from the web interface, mailman complains that the user 
doesn't exist. Same if I try it via the mail interface.

I've tried every combination of quotes and escapes I can think of.

So any ideas, anyone?

Thanks
Rachel