Believing that a Morgan shot had gone for four, Bell (on 137) abandoned his crease and was chatting to his batting partner when Abhinav Mukund took the bails off.
Geoffrey BoycottFormer England batsman and BBC summariser
“India have been smashed out of the game and it will take a supreme effort for them to save it, let alone win it ”
As the England pair headed for the pavilion, India appealed for a run out which was upheld by the umpires after TV replays.
With the crowd shouting their displeasure at the decision, the two teams held talks during the interval and India captain Mahendra Dhoni sportingly agreed to withdraw the appeal.
The sight of Bell running out after tea was greeted with cheers and applause, but the stand-in number three looked a touch subdued after being reinstated, scoring just 22 more runs before he was caught at slip off Yuvraj Singh.
As he left the field, he shook hands with several of the India players, underlining England's appreciation for Dhoni's gesture.
Following Bell's dismissal, England lost Morgan and Jonathan Trott - batting down the order because of a shoulder injury - to the new ball.
But any suggestion that the momentum might be swinging back India's way was dismissed out of hand in a brilliant unbroken partnership of 102 between Prior and Tim Bresnan (47 not out).
Prior tore into the India attack, hammering 64 off 55 balls to leave the hosts in prime position to go on and win the game, and take a 2-0 lead in the four-match series.
With England in a position of such supremacy, it would be easy to forget that they began the day on 24-1 - still 43 runs adrift of India.
They also lost Andrew Strauss early on, the England skipper's tentative prod at Ishant Sharma taken by Dhoni behind the stumps.
Strauss has still not scored a fifty in eight Test innings this summer and with his injured left-arm nemesis Zaheer Khan set to return to the India side at Edgbaston there is plenty of hard work ahead.
Malcolm AshtonTest Match Special scorer
Ian Bell has now scored a century against all the other eight current Test-playing nations. Only four players have scored one against nine, when Zimbabwe were still in the fold: Gary Kirsten, Sachin Tendulkar, Rahul Dravid and Marvan Atapattu
Bell, in contrast, looked in superb touch as he motored to fifty off 72 balls with successive fours off Sharma. Pietersen made a much more watchful start to his innings, taking 52 balls before finding the boundary with a paddle-sweep off Harbhajan Singh.
Lunch seemed to induce a change of mindset, with Pietersen opening his shoulders and smashing Sharma for three fours in an over and getting to a half-century off 98 balls.
Bell played and missed at the first ball after the interval but was soon back into rhythm as he brought up his 15th Test hundred to complete a set against all eight Test-playing nations.
Pietersen made 63, but after appearing to get distracted by someone moving behind the bowler's arm, he took a swipe at Sreesanth and was caught behind.
Morgan batted positively from the outset, striking eight fours and a six as he and Bell took England's lead well past the 250 mark.
Their partnership of 104 - punctuated by Bell's astonishing reprieve - could yet turn out to be the decisive in the outcome of the match.
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