single flash

[SmartWombat]

I ran into a big problem a the Autisport show, the drivers were doing autograph signings at a desk which had a glass top.
How would you cope with that, given that it's a public event and the drivers are signing for the fans rather than having a photo call for the press?

Getting close works of course, so that the flash doesn't illuminate the desktop and you don't get weird reflections and shadows in the background.

I tried just one experiement with bounce flash off the wall behind, and extending the catchlight panel to give a little bit more diffuse light.
Did it work?

More important though, what would you do with only a single flash in this situation?