zabbix-server-mysql dist-upgrade (1.6.4 -> 1.8.1) fails because of SQL patch problem

Debconf states that the database must be manually upgraded using a patch during Karmic -> Lucid dist-upgrade before Zabbix 1.8.x will run...

Attempting the SQL patch fails:
sudo sh -c "zcat /usr/share/doc/zabbix-server-mysql/examples/patch.sql.gz | mysql -D zabbix"

ERROR 1061 (42000) at line 68: Duplicate key name 'graphs_items_1'

Zabbix will then start with the following errors at the login page:
Error in query [SELECT g.usrgrpid FROM usrgrp g, users_groups ug WHERE ug.userid = 1 AND g.usrgrpid = ug.usrgrpid AND g.debug_mode = 1 LIMIT 1 OFFSET 0] [Unknown column 'g.debug_mode' in 'where clause']
mysql_fetch_assoc(): supplied argument is not a valid MySQL result resource[/data/srv/www/htdocs/include/db.inc.php:546]
mysql_free_result(): supplied argument is not a valid MySQL result resource[/data/srv/www/htdocs/include/db.inc.php:548]

This can be worked around by running with the force option to get MySQL to complete the schema update and restarting Zabbix:

sudo sh -c "zcat /usr/share/doc/zabbix-server-mysql/examples/patch.sql.gz | mysql -f -D zabbix" # note -f 'force' is required.
sudo /etc/init.d/zabbix-server restart