diff --git a/mysite/code/Jobs/UrgentExpirationReminder.php b/mysite/code/Jobs/UrgentExpirationReminder.php
new file mode 100644
index 0000000..0a17458
--- /dev/null
+++ b/mysite/code/Jobs/UrgentExpirationReminder.php
@@ -0,0 +1,122 @@
+<?php
+
+use Maknz\Slack\Attachment;
+
+/**
+ * Class for posting to Slack the certificates expiring soon.
+ */
+class UrgentExpirationReminder implements CronTask
+{
+    use CronTaskUtilities;
+
+    /**
+     * @return string Cron expression
+     */
+    public function getSchedule()
+    {
+        return '0 * * * *';
+    }
+
+    public function process()
+    {
+        $siteConfig = SiteConfig::current_site_config();
+        if (!defined('SLACK_WEBHOOK_URL') || !$siteConfig->SlackPostDailyUpdate) {
+            $this->log('Slack not enabled, task not running', SS_Log::INFO);
+
+            return;
+        }
+
+        $domains = Domain::get()->filter(['Enabled' => 1]);
+        $this->log('Number of existing domains: '.$domains->count(), SS_Log::INFO);
+
+        $alertDays = [
+            'P1' => $siteConfig->OpsGenieDaysUntilP1,
+        ];
+
+        $startAlerting = max(array_values($alertDays));
+        $alerts = [];
+
+        foreach ($domains as $d) {
+            if (!$d->CurrentCertificate()->exists()) {
+                $this->log('Skipping '.$d->Domain.' as it doesn\'t have a certificate', SS_Log::INFO);
+
+                continue;
+            }
+
+            $cert = $d->CurrentCertificate();
+
+            $this->log('Checking '.$d->Domain, SS_Log::INFO);
+            $this->log('Days until expiration: '.$cert->DaysUntilExpiration, SS_Log::DEBUG);
+
+            // Skip if we're outside the alerting threshold
+            if ($cert->DaysUntilExpiration > $startAlerting) {
+                continue;
+            }
+
+            $priority = $this->closestNumber($cert->DaysUntilExpiration, $alertDays);
+            $this->log('Current alert priority: '.$priority, SS_Log::DEBUG);
+
+            // Create the line for this domain with a link to open it in the tool
+            $line = sprintf(
+                '%s, expires <%s/admin/domains/Domain/EditForm/field/Domain/item/%s/edit|%s>',
+                $d->Domain,
+                Director::absoluteBaseURL(),
+                $d->ID,
+                $cert->ValidTo
+            );
+
+            if (Freshdesk::IsAvailable() && $d->FreshdeskID) {
+                $line .= sprintf(
+                    ', <%s/helpdesk/tickets/%s|open in Freshdesk>',
+                    FRESHDESK_DOMAIN,
+                    $d->FreshdeskID
+                );
+            }
+
+            $alerts[$priority][] = $line;
+        }
+
+        if (empty($alerts)) {
+            $this->log('No domains to alert to, bailing', SS_Log::INFO);
+
+            return;
+        }
+
+        $this->log('Sending the hourly urgent Slack certificate expiration reminder', SS_Log::INFO);
+
+        // Sort the array by the priority
+        ksort($alerts);
+
+        $settings = [
+            'username' => SiteConfig::current_site_config()->Title,
+            'channel' => SiteConfig::current_site_config()->SlackChannel,
+            'icon' => SiteConfig::current_site_config()->SlackEmoji,
+        ];
+
+        $client = new Maknz\Slack\Client(SLACK_WEBHOOK_URL, $settings);
+        $attachments = [];
+
+        foreach ($alerts as $priority => $lines) {
+            $attachments[] = new Attachment([
+                'color' => $this->alertColor($priority),
+                'author_name' => sprintf('%s (%d days or less)', $priority, $alertDays[$priority]),
+                'text' => implode("\n", $lines),
+                'mrkdwn_in' => ['text'],
+            ]);
+        }
+
+        $client->setAttachments($attachments)->send('The following certificates are about to expire and need to be dealt with ASAP. This alert is sent every hour by <https://platform.silverstripe.com/naut/project/locksmit|Locksmith>.');
+    }
+
+    /**
+     * Returns the color for the alert priority when posting to Slack.
+     *
+     * @param $priority
+     *
+     * @return string Hex color code
+     */
+    protected function alertColor($priority)
+    {
+        return '#EF0909';
+    }
+}