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.

London Underground getting into the spirit of BluesFest with this impressive announcement board at North Greenwich Station.

I really do owe Beth Hart an apology. For some reason, my limited exposure to Beth's material had left me thinking she was a one-note blues screamer in the Janis Joplin mould. Frankly, I couldn't have been more wrong as there are many layers to Beth and her sound. The lady can sing, actually, I'll rephrase that as it is damning her with faint praise, her voice has incredible power and clarity and tonight she was as good as anyone I've seen. An early start time resulted in far too many empty seats as Beth began her set but this was slowly but surely rectified during her ninety minutes on stage. Beth readily admitted to being a little nervous at the beginning but you'd hardly notice as she demonstrated her range switching effortlessly from bluesy stompers, via jazzy torch songs, to funky workouts without missing a beat with 'Baddest Blues' one of many highlights. Early in her set, she clambered down off the stage to perform 'Your Heart Is as Black as Night' standing at the crash barrier "I feel safe if I'm closer" she claimed.

The sound in the vast O2 arena was fantastic, crystal clear; Beth is one of those singers who really has her microphone technique down, although on occasion she sounded pretty great without due to her power. With her top-notch band featuring Jon Nichols (guitar), Bob Marinelli (bass) & Bill Ransom (drums) in tow Beth was able to switch up the setlist as the mood took her and the audience demanded. An engaging presence on stage Beth frequently referred to her struggles with addiction and illness over the years in a refreshingly open manner which adds to the strength of songs such as 'Bottle Of Jesus' but the highlight of the evening had to be a solo Beth at the piano for incredible renditions of 'My California' and 'Leave A Light On'. Beth Hart is one of a kind and I will be looking to check out her back catalogue much more carefully based on her performance at BluesFest.

Closing tonight's BluesFest we were treated to the Zac Brown Band from Atlanta, Georgia. Zac and his seven-piece band are difficult to pigeonhole. If someone asked me who they sound like, or what genre they work in, a straight answer would be very difficult. Zac Brown Band are a country act to all intents and purposes — they'd previously headlined the Country 2 Country festival here at the O2 — but that is just the beginning of the story. If you took the Eagles, Old Crow Medicine Show, The Allman Brothers Band and the best covers band you've ever heard and mixed them up in a blender you'd have the beginnings of the story. At the end of the day, the Zac Brown Band have the vocal ability and the musical chops to pretty much play anything and they demonstrated that tonight.

Zac and the boys were delayed by 10-15 minutes, never ideal with an obvious curfew, due to technical issues and were looking to make up for lost time as they blazed through an opening 'Whiskey's Gone' in a set that was big on the hits with the likes of 'Chicken Fried', and 'Toes' such crowd-pleasing tunes, 'Adios and Vaya con Dios' will never get old if you're looking for audience participation. The band are known for delivering a range of cover tunes and Kings Of Leon's 'Use Somebody' with that ridiculously catchy vocal hook is tailor-made for an arena. A bone-crunching 'Enter Sandman' with John Driskell Hopkins on vocals and fiddle player Jimmy De Martini stepping on the wah-wah for a solo was a blast. Pride of place though must go to a stunning version of the Allman's 'Whipping Post', Clay Cook's vocal on this classic would have the late Gregg Allman looking down and smiling broadly as Zac and Coy Bowles traded extensive guitar licks. It's fantastic to see three guitarists in the best traditions of Southern rock ala Lynyrd Skynyrd or Molly Hatchet especially when the band has the ability to deliver harmonies on 'Free' to rival the Eagles. A special mention for a personal favourite 'Cold Weather' which had the whole arena illuminated by mobile phone screens (some of us remember lighters but hey-ho) without the band asking for such things, was beyond cool and Zac looked very impressed. A quick run through of the Beastie Boys 'Sabotage', which sounded like the Red Hot Chili Peppers on speed, was great fun with Jimmy now in the role of head MC. Possibly this might have been a tune too far for the more die-hard country fans in the place but hell it sure was great noisy fun.

BluesFest came up trumps tonight at the O2 with two acts on peak form blessed with fantastic sound. As I said earlier I'll definitely be taking a good listen to the Beth Hart catalogue and I really do hope that Zac Brown Band make it back to the UK soon as I'd love to see them play one of their famed extended shows, where they get to stretch out musically and jam a little, but a great show is a great show and I’m already looking forward to BluesFest 2019.