A few years ago when I still watched F1 I came to realise that Martin Brundle is a terrific guy to have in the box. Not only does he have the experience of modern day F1 racing, he also knows (knew...) a lot of the drivers on the grid and had a fantastically dry sense of humour. "Michael eased past to lap that Sauber as if it wasn't there, much easier than Coulthard found it. I'm sure it's pure coincidence that it's got a Ferrari engine in it". He also used to have Murray Walker in stitches sometimes when he'd correct his mistakes with a sarcy comment.
Because he's driven most of the tracks on the circuit, he can give you a real insightful talk through when riding on-board with a driver. He doesn't just tell you what you can see, he tells you what is going through the driver's mind at the time, and prepares you for upcoming bends, cars etc.