Is it possible to stream BBC Iplayer live TV to Google Nest hub?

I set up Google cast as per the docs and streaming recorded TV is fine.
The docs mention the optional parameter is_live so I guessed that it should be possible to stream live TV. I had to take a few goes at guessing how to use the is_live parameter but adding “true” seems to work. However the http address for live TV is a different structure to recorded:

Live TV address:
BBC iPlayer - Watch BBC One live

Recorded TV address:
BBC iPlayer - The Met - Series 4: Episode 1

The docs explain how to choose the episode ID but not how to select a live stream.
Has anybody found a way to make it work please?