NSURLCache bypasses HTML5 video tag

I have an NSURLCache descendent working with a UIWebView. I load a web page in the WebView and can intercept all of the HTTP requests it makes (and cache locally to the documents directory). This works for inline images, javascript references and css references and for all url calls within CSS. HOWEVER this does not pick up the call from an HTML5 video tag....开发者_运维问答

I am left with all required files for a page EXCEPT the videos which causes me an issue when trying to view the webview offline (after caching).

Does anyone know why NSURLCache doesn't work with VIDEO tags and / or how I can get this to work!??!?!