David Gilmour (Pink Floyd) and Brian May?

I found this video on YouTube: http://www.youtube.com/watch?v=wFHL5b7dIpE&mode=related&search=

It's Pink Floyd's David Gilmour and Brian May jamming on Deep Purple's Smoke on the Water. Has anyone ever heard of this? Or know anything about it? It appears to be in the late-80's, right after Pink Floyd's Momentary Lapse of Reason tour,

1989 - Rock Aid Armenia, released as a single with a compilation album & VHS of the same name.

Also featured -

Ritchie Blackmore
Chris Squire
Keith Emerson
Roger Taylor
Brian Adams
Bruce Dickinson
Ian Gillan
and others

and a mr Paul Rodgers