Thanks for the response. No redirects that I can see in config files.

The Umbraco back end looks like this:

--> Home
|| en
*Website configuration (en)
|| de
*Website configuration (de)
||Group
*WEbsite configuration (group)

(sorry, don't seem to be able to upload an image) The template on Home is a redirect with the following code:

@using USNStarterKit.USNHelpers;
@{  
    string redirectUrl = "/en";
    LinkInfo linkInfo = USNUrlHelper.GetSingleUrlFromUrlPicker(Model.Content.GetPropertyValue<UrlPicker>("redirectTo"));
    @Convert.ToString(Model.Content.GetPropertyValue<UrlPicker>("redirectTo"))
    if (linkInfo != null) {
        if (linkInfo.LinkURL != String.Empty) { 
            redirectUrl = linkInfo.LinkURL;
        }
    }

    Response.Redirect(redirectUrl);
}

Which is designed to direct people from example.com to example.com/en to start. So I did think this might be an issue. However even when this page is unpublished, the issue is still happening, even after app pool stop/start. I have tried setting Culture/Hostnames of this node to example.com but it makes no difference