Renaming the Aegir hostmaster site itself

WARNING: Be sure to have a good backup (which you can restore) before attempting this.

manually edit the crontab for aegir to stop the periodic execution of the command 'hosting-dispatch' (the drush command 'hostmaster-pause' did not exist on my system)
delete the hostmaster site (drush @hostmaster provision-delete)
change the alias (drush provision-save @hostmaster --uri=hostmaster2.example.com --aliases=hostmaster.example.com)
deploy the backup (drush @hostmaster provision-deploy /var/aegir/backup/hostmaster.example.com...tgz)
checked that all changes appeared correct - YES
Reneabled the hosting-dispatch task by editing the crontab again
ran a verify task against the new hostmaster site. Noticed that the site is listed on the site page with the old domain name. The verify failed.
Found that the verify task had created a new entry in the hostmaster-6.x-1.7/sites directory for the old domain name. I removed this created directory. I found and edited (using phpMyAdmin) the relevant entries in the node and node revision tables for the hostmaster site to update the domain name (change the title field). The hosting_site_alias table may also need to be updated if you have site aliases.
The verify task also seemed to have regressed the @hostmaster alias file (~/.drush/hostmaster.alias.drushrc.php) as it had the URI and aliases details from the old site back in it. I edited this file to return these items to their new values.
The verify task now completed successfully and all seems to be working correctly.