Hello Graham,
The best way is to get the link from the poster of the video. The poster of the video has the URL of the video exposed in a “Download” link when they go to their respective video page.
At this time, we don’t expose the source URL of videos publicly. Some obscurity helps detract bots from crawling, and downloading all the videos, even though it be just a little. I’m sure you can imagine, it’s rather difficult to fight bots mass downloading our content. Even YouTube has difficulty, and changes the location of their videos regularly. Site sucking bots bog down our network, and cost money to serve.
If you can’t get the URL from the video owner, there are ways to see the URL, which is not news to people in the IT field, so I’m not concerned to publish it. You can check the network activity in your browser tools when you play the video, this will show the source URL. e.g.:
https://getfirebug.com/wiki/index.php/Net_Panel
Hope this helps.
Abraham