Some replays are suggesting that Root was the victim of some uneven bounce. Indeed, the following ball of the next over, delivered by Siriwardana, kept low. Unusual signs on day one. Not great for the team set to bat last (Sri Lanka).  

Andrew Samson
BBC Test Match Special statistician

"Seven of the last eight times Joe Root has passed 50, he's got out before he got to 100."

Looking again, Root actually played that with both feet off the ground. He was trying to take a delivery from outside the off stump through the leg side. A hint of extra bounce? In frustration, he punched his bat as he stomped up the pavilion stairs. Jonny Bairstow, currently with more form than the Kray twins, is the new man.

Phil Tufnell
Ex-England spinner on BBC Test Match Special

"Root was trying to get across and play a top-spin to mid-wicket or square leg, but as he's tried to work it into the leg side, the ball's bounced more than he expected and he's got himself in a tangle. He should have looked to play the hook. It reminded me of a David Warner dismissal."

Jonathan Agnew
BBC Test Match Special

"He walks off looking suspiciously at the pitch in high dudgeon, but he's missed a hundred there. Got in an absolute tangle."

Phil Tufnell
Ex-England spinner on BBC Test Match Special

"Herath looks like he knows his way around a tea trolley, but with nearly 300 Test wickets, he clearly knows his way around left-arm spin too."

That's a bad un from Herath, too far down the leg side to allow Root a paddle fine for four. From absolutely nowhere, Root has dabbed, nudged, worked and scampered his way to the verge of a 10th Test ton. That was only his fifth four.

Ben Eveling: We still doing quiz shows? Ramprakash in the attic: our man lurks in people's lofts and springs out at inopportune moments.

Martin Cookson: Through the Keyhole. Colonoscopy-based treasure hunt show feat former Eng & Kent batsman Robert Key. Or parts of him, anyway.

Michael Jones: Songs of Fraser: ex-England legend Angus takes us through his CD collection.

Who says it's cold in the North? There's a chap in the stands eating an ice cream. Admittedly, he's wearing a cardigan thicker than a duvet, but the sun is still shining bright enough for the floodlights to have been turned off. Nuwan Pradeep, stubble undoubtedly longer than when we began this morning, is half-edged, half-guided through third man by James Vince for four.

Neil Saffer

Image source, PA

Joe Root must be a nightmare on a long car journey. He's unable to sit still for a moment. Herath thinks he might be in with a sniff of a maiden, but Root has the dancing feet of Fred Astaire to work through the leg side. Genuine sunshine now. Players even casting shadows.

Jonathan Agnew
BBC Test Match Special

"Herath's bowled so many overs that we could actually finish on time today, which doesn't happen often."

Players are back out at a bright Chester-le-Street. Amazingly, there are only 29 overs left in the day. We might even finish on time. Rangana Herath to Joe Root...

I'll stop now.

Or Rooting Stars, where Joe Root gains access to the homes of celebrities and has a good nose around.

Or Fort Boycott, where Geoffrey (and Melinda Messenger) present challenges involving rhubarb, uncovered pitches and corridors of uncertainty

Thanks, James. Are we still talking cricketing games shows? Am I too late to mention Ready, Steady, Cook, where Alastair has to make a meal with whatever is in your fridge?

Right, here to take you through the evening session, I present to you Stephan Shemilt.

James Vince has played nicely so far - here's one slightly fortuitous moment, when he top-edged a pull that went for four.

BBC Test Match Special

But first TMS are hearing about when England batsman James Taylor - who recently had to retire with a serious heart problem - met up with ex-footballer Fabrice Muamba, whose heart stopped during a match.

You can hear the full programme on BBC Radio 5 live at 21:00 BST next Wednesday, 1 June.