By Jonathan Agnew BBC cricket correspondent

Alastair Cook's unbeaten 104 steers England to a big lead over India on the fourth day in Nagpur.

India will need to survive session by session as they battle to save the match

Alastair Cook might be new to Test cricket, but he is proving to be a quick learner and having scored a century on debut joins a list of England players headed by WG Grace.

He will never have encountered anything like Kumble and Harbhajan operating in tandem on a wearing pitch before but apart from one or two minor alarms, he played an excellent innings.

A more experienced batsman might have been able to press on a little more as the day came towards its end, but this match will stand Cook in great stead.

His opening partnership with Strauss was especially important, and by the time they were parted England were 165 ahead.

India already knew their chances of victory had gone.

Technology has made decision-making easier for umpires - especially run outs and stumpings - and even opponents of its use, like me, are finding it increasingly difficult arguing against those who favour its introduction on a more widespread basis.

Day four report

But there are still occasions when the third umpire, despite the benefit of as many slow motion replays as he wants, makes a mistake.

Kevin Pietersen was very fortunate indeed to be given the benefit of the doubt after apparently squeezing back a return catch to Anil Kumble.

Numerous replays from several angles all appeared to confirm that the ball had come from the bottom of his bat, and that he should have been given out for 36.

Technology was introduced to eliminate mistakes, and it is doubly frustrating when bad decisions are made.

It was vital England wrapped up the Indian innings as quickly as possible at the start of play, and Matthew Hoggard needed just five balls to do so.

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Replays suggested that Sreesanth�s bat might have touched the ball before it hit his pad - and England have enjoyed the rub of the green in this game.

This gave England a useful lead of 70 and Hoggard the superb figures of 6-57.

India will need to survive session by session as they battle to save the match.

England's bowlers have to be patient because the pitch is not a minefield, but the ball is starting to misbehave and new batsmen will find it difficult to settle in.

It will be fascinating to see how Monty Panesar performs with men around the bat, while Flintoff�s captaincy will be tested if Sehwag gets India away to a flying start.