UPDATE: Of course! It was from the 2008 Spirit Of Life Award Dinner on October 15 where she covered "I Second That Emotion" from Doug Morris. Succo provides this link, for which he deserves muchos cudos. :-)
Here's the article about it I remember reading at the time...
That was fun. Perhaps we should do it again!
The date said 15th Oct 2008 but that could be a red herring. My gut feeling is a private showcase that at the time we didn't hear much about but I suppose it could have been a tv appearance with a snazzy outfit like that.
Answers on postcard... o actually, since Royal Mail are striking left right and centre, (but the BBC is BIZARRELY NOT TELLING ANYONE ABOUT IT - I sent a first class large letter to London Sept 26th and they got it yesterday!) you'd better leave a comment instead.