That was Griffiths's 16th goal of the season. Not a bad return.

Stuart Armstrong works the ball across to Scott Brown on the edge of the United box and the Celtic captain lays the ball off to Stefan Johansen who, showing the touch and vision that has won admirers this season, rolls the ball to Leigh Griffiths on the right side of the box and he arrows a shot across Radoslaw Cierzniak and into the net at the Shed End.

And we have a second half now being played...

Former Celtic goalkeeper Pat Bonner

"I thought Dundee United got a lot of good blocks in. Celtic have got in down the left a few times but down the right they haven't done anything. (Full-back) Adam Matthews has been up the pitch maybe only once. Celtic's passing was poor. The groundsmen are watering the pitch now so the ball should move around better. Celtic's tempo and movement has to increase."

Image source, SNS

Celtic's Kris Commons has been busy taking his team's corner kicks and free-kicks and has had the occasional shot at goal but has been well watched by the likes of John Souttar sitting in front of United's two central defenders.

Image source, SNS

Celtic skipper Scott Brown takes his punishment from referee Willie Collum after a challenge on John Rankin, a tackle BBC Radio Scotland pundit Willie Miller argues would have been applauded in his playing days with Aberdeen.

David Mowat on Facebook: "You wonder how attractive the prospect of European Football would be to United, with qualifying games as early as June against a Fish Factory team from the Lofoten Islands or the like?"

Well, no goals in the opening 45 minutes but there was entertainment aplenty, albeit seldom resulting in a shot on goal. The best moment of the half was Robbie Muirhead's cracking shot that was tipped over by Celtic goalie Craig Gordon.

Brian MacNaughton: "#bbcscotfootball Brown and Izaguirre are the two most overrated players in the SPL."

Chris Erskine tries his best to get clear of the green and white hoops and has the scent of goal but Virgil van Dijk gallops in to take the ball of his toe. That's a few times in this match that the Dutchman has been able to recover a situation thanks to his pace.

Nir Bitton stands on the ankle of United's Blair Spittal, who rolls around in agony until the pain subsides. Bitton is upbraided by Willie Collum and play restarts.

United centre-half Jaroslaw Fojut springs to head away Kris Commons' in-swinging corner kick from the right. Celtic win the ball back in the final third but can't find an opening and eventually the attack peters out.

David de la Fawkes: "#bbcscotfootball Scott Brown has only been booked 12 times this season? Amazing......"

Five minutes until half-time.

Image source, SNS

Celtic striker Leigh Griffiths and United goalkeeper Radoslaw Cierzniak compete for a long ball forward. Griffiths clipped the Pole's foot after the goalie had cleared the ball but all ended amicably.

Blair Spittal and Paul Dixon tear Celtic apart down the left and win a corner, but the visitors clear and break swiftly to win a corner at the other end. Stuart Armstrong sends in the delivery for Celtic and United hoof it clear all the way to Craig Gordon at the other end.

EdinburghTom: "The risk for Dundee Utd is that any players doing well 2day will be playing against them in this fixture next season #bbcscotfootball"

Former Aberdeen captain Willie Miller

"That would have been an excellent challenge in my day."

Scott Brown is booked by Willie Collum for a meaty challenge on John Rankin, the Celtic captain's 12th booking of the season. He'll be hoping he doesn't get a baker's dozen today. He slid in and with studs up got the ball away from the United midfielder but also sent Rankin spinning into the air.