Hi there! I see you're having trouble with closed captioning on BritBox. To help you better, could you tell me a bit more about the issue? For example, is the closed captioning option not appearing at all, or does it appear but doesn't show the subtitles? Also, what device or browser are you using to watch BritBox?

Since you mentioned your device is WebKit on Windows 10, here are a few general steps we can try first to get closed captioning working:

1. Check BritBox subtitle settings: While playing a show, look for the "CC" (closed caption) or "Subtitles" option in the player controls and make sure it's turned on.

2. Verify browser settings: Sometimes browser settings can interfere with captioning. In WebKit, try refreshing the page, and also check that you haven’t disabled any accessibility features or media permissions that affect subtitles.

3. Clear browser cache: Cached data can sometimes cause display issues. Clear your browser cache and cookies, then reload BritBox.

4. Update your browser: Make sure your WebKit browser is updated to the latest version to avoid compatibility problems.

5. Restart your device: Restarting your Windows 10 computer can often resolve temporary glitches.

If these steps don’t help, please let me know if the closed caption problem is consistent across all shows or only certain titles, and if you notice any patterns like captions disappearing after a certain time. That info will help me pinpoint the issue better!

Are you comfortable trying these steps? I'm here to guide you through them.