'If the system is only used by a single Organisation then this can be defaulted/hidden
- if-appropriate can also use lazy settings to set this from the user.organisation_id'

def get_org_default_organisation(self):

    default_organisation = self.__lazy('org', 'default_organisation', default=None)
    if default_organisation:
        if (not isinstance(default_organisation, (int, long))):
            default_organisation_id = current.session.s3.default_organisation_id
            if default_organisation_id:
                default_organisation = default_organisation_id
            else:
                table = current.s3db.org_organisation
                org = current.db((table.name == default_organisation)).select(table.id, limitby=(0, 1)).first()
                try:
                    default_organisation = org.id
                    current.session.s3.default_organisation_id = default_organisation
                except:
                    current.log.error(('Default    Organisation    not    found:    %s' % default_organisation))
                    default_organisation = None
    return default_organisation
