diff --git a/.github/workflows/main-build-and-deploy.yml b/.github/workflows/main-build-and-deploy.yml
index d54a70cffd..cf73dfdb2c 100644
--- a/.github/workflows/main-build-and-deploy.yml
+++ b/.github/workflows/main-build-and-deploy.yml
@@ -103,7 +103,7 @@ jobs:
     uses: ./.github/workflows/template-ui-tests.yml
     with:
       deploy_url: ${{ needs.deploy-staging.outputs.url }}
-      tests_to_run: "images seo-noindex" # staging slot should not be indexed
+      tests_to_run: "images seo-noindex gtm-tracking" # staging slot should not be indexed
 
   swap-staging:
     name: Swap staging with production
diff --git a/.github/workflows/pr-deploy-command.yml b/.github/workflows/pr-deploy-command.yml
index 4ef70ee25e..2d66a9cd5f 100644
--- a/.github/workflows/pr-deploy-command.yml
+++ b/.github/workflows/pr-deploy-command.yml
@@ -205,7 +205,7 @@ jobs:
     uses: ./.github/workflows/template-ui-tests.yml
     with:
       deploy_url: ${{ needs.pr-deploy.outputs.url }}
-      tests_to_run: "images seo-noindex"
+      tests_to_run: "images seo-noindex gtm-tracking"
 
   prLighthouseInsights:
     name: Run PR Lighthouse Insights
diff --git a/app/components/google-tag-manager.tsx b/app/components/google-tag-manager.tsx
new file mode 100644
index 0000000000..2752f1bab0
--- /dev/null
+++ b/app/components/google-tag-manager.tsx
@@ -0,0 +1,33 @@
+import Script from "next/script";
+
+/**
+ * GTM split out of @next/third-parties' <GoogleTagManager>, which only exposes an
+ * afterInteractive load. The dataLayer is created and `gtm.start` pushed eagerly, so early
+ * `sendGTMEvent` / `dataLayer.push` calls (e.g. the eventbrite_order_complete conversion) queue
+ * and flush once GTM arrives — but gtm.js itself loads on idle (lazyOnload) instead of during
+ * hydration, keeping the container's marketing tags (GA4/Ads/FB/Hotjar) out of the critical window.
+ * sendGTMEvent from @next/third-parties keeps working: it pushes to window.dataLayer directly and
+ * doesn't depend on this component rendering.
+ * Retiming the individual tag triggers is GTM container config, not code — see #4908.
+ */
+export const GoogleTagManager = ({ gtmId }: { gtmId?: string }) => {
+  if (!gtmId) return null;
+  return (
+    <>
+      <Script
+        id="gtm-datalayer-init"
+        strategy="afterInteractive"
+        dangerouslySetInnerHTML={{
+          __html:
+            "window.dataLayer=window.dataLayer||[];window.dataLayer.push({'gtm.start':new Date().getTime(),event:'gtm.js'});",
+        }}
+      />
+      <Script
+        id="gtm-script"
+        data-ntpc="GTM"
+        strategy="lazyOnload"
+        src={`https://www.googletagmanager.com/gtm.js?id=${gtmId}`}
+      />
+    </>
+  );
+};
diff --git a/app/layout.tsx b/app/layout.tsx
index 5057a96d34..6f7f971861 100644
--- a/app/layout.tsx
+++ b/app/layout.tsx
@@ -2,7 +2,6 @@ import { PhishingBanner } from "@/components/phishing-banner/phishing-banner";
 import { MegaMenuWrapper } from "@/components/server/MegaMenuWrapper";
 import { AppInsightsProvider } from "@/context/app-insight-client";
 import { EventInfoStatic } from "@/services/server/events-types";
-import { GoogleTagManager } from "@next/third-parties/google";
 import dayjs from "dayjs";
 import advancedFormat from "dayjs/plugin/advancedFormat";
 import isBetween from "dayjs/plugin/isBetween";
@@ -14,6 +13,7 @@ import dynamic from "next/dynamic";
 import { inter } from "@/lib/fonts";
 import "styles.css";
 import client from "../tina/__generated__/client";
+import { GoogleTagManager } from "./components/google-tag-manager";
 import LandingPageCapture from "./components/landing-page-capture";
 import { MenuWrapper } from "./components/MenuWrapper";
 import PageLayout from "./components/page-layout";
diff --git a/ui-tests/gtm-tracking.spec.ts b/ui-tests/gtm-tracking.spec.ts
new file mode 100644
index 0000000000..2493e938ab
--- /dev/null
+++ b/ui-tests/gtm-tracking.spec.ts
@@ -0,0 +1,64 @@
+import { test } from "@playwright/test";
+
+/**
+ * Regression guard for #4908: GTM now loads on idle (lazyOnload) instead of during hydration.
+ * The deferral must NOT drop tracking, so this asserts on a running site that:
+ *   1. gtm.js is still fetched (on idle) — the container/beacons aren't silently disabled.
+ *   2. window.dataLayer is initialised with the gtm.js start event, so early
+ *      sendGTMEvent / dataLayer.push calls (e.g. the eventbrite_order_complete conversion)
+ *      queue and flush once GTM arrives.
+ *
+ * The downstream marketing beacons only fire with the real GTM container + NEXT_PUBLIC_GOOGLE_GTM_ID
+ * present, so those stay manual dashboard checks: GTM Tag Assistant (tags fired + order), GA4
+ * Realtime, Meta Events Manager -> Test Events, Hotjar dashboard. Corresponding network beacons:
+ * GA4 google-analytics.com/g/collect, Ads googleads.g.doubleclick.net/pagead,
+ * FB facebook.com/tr?, Hotjar *.hotjar.io.
+ *
+ * Run against a server with the GTM id set (e.g. HOST_URL=https://www.ssw.com.au pnpm exec
+ * playwright test ui-tests/gtm-tracking.spec.ts); without the id the beacon assertion self-skips.
+ */
+test("GTM still loads and dataLayer queues after deferral", async ({
+  page,
+}) => {
+  const gtmRequest = page
+    .waitForRequest(
+      (req) => req.url().includes("googletagmanager.com/gtm.js"),
+      { timeout: 15000 }
+    )
+    .catch(() => null);
+
+  await page.goto("/", { waitUntil: "load" });
+
+  // lazyOnload requests gtm.js on idle after load; resolves to the request, or null on timeout.
+  const request = await gtmRequest;
+
+  // Tracking not dropped: reaching here (not skipping) means gtm.js was fetched after the deferral.
+  // No id on this server (e.g. local dev) => no request => skip the live assertion cleanly.
+  test.skip(
+    request === null,
+    "NEXT_PUBLIC_GOOGLE_GTM_ID not set on this server — skipping the live GTM beacon assertion (verify tags via the manual dashboard checks in the file header)."
+  );
+
+  // dataLayer queuing: the eager init created the array and pushed gtm.start, so events sent
+  // before GTM finishes loading are queued rather than lost. Poll rather than sample once — the
+  // init runs on afterInteractive, so it may land a tick after the gtm.js request is observed.
+  await page
+    .waitForFunction(
+      () => {
+        const w = window as unknown as {
+          dataLayer?: Array<{ event?: string }>;
+        };
+        return (
+          Array.isArray(w.dataLayer) &&
+          w.dataLayer.some((e) => e?.event === "gtm.js")
+        );
+      },
+      null,
+      { timeout: 5000 }
+    )
+    .catch(() => {
+      throw new Error(
+        "window.dataLayer never received the gtm.js start event — early events would be dropped."
+      );
+    });
+});