On what feels like the first cold night of the year your RGM scribe is at the O2 in London for the Zac Brown Band and Beth Hart. Tonight's show is part of the annual BluesFest which has found a home at the O2 and is now in its sixth year. With ticket in hand, airport-style security negotiated and a sharp intake of breath at the beer prices I'm in my seat bright and early for Beth Hart to get things started.