Steven Finn does not have a bat sponsor at the moment. Someone has missed out on almost five hours of valuable airtime after Finn surprised everyone, including a former team-mate and his current captain, with his performance on the final day in Dunedin.

He had emerged shortly before the close of the fourth day, for the first time in the role, after Alastair Cook edged behind to end an opening stand of 231. His job was to protect Jonathan Trott so that the specialist batsman could negotiate the final day. In the end, Finn outlasted Trott and Kevin Pietersen during a 203-ball stay.

Given that Nick Compton fell shortly after the first hour, Pietersen departed cheaply and two quick wickets fell after tea it is not inconceivable that, had Finn failed, or even been dismissed a couple of hours earlier, England may not have saved the match. When he went from 53 to 54 after fifty dot balls there was a slightly embarrassed look on his face. There was no need.

The secret behind his success? According to Cook, it's a bribe that he did not want to reveal but that Finn, himself, later said was four cases of wine from the captain and James Anderson, two from each for surviving two sessions.*

"Bribing Steven, that if he got through a certain number of overs, seemed to work so we might apply that again. It will remain a secret but he gets well rewarded for his efforts today. He's done very well out of a few of the lads.

"The way Steven applied himself was fantastic, I certainly didn't know he had that in him - I don't think he did either - but it shows when you really put your mind to something and are really disciplined on a flat wicket anyone can make themselves hard to get out."

Brendon McCullum, who spent time with Finn during his stint in New Zealand domestic cricket, was equally surprised about the innings. "He played at Otago and I've seen his batting before. He's certainly worked on it."

The knock was a product of lengthy net sessions, particularly with batting coach Graham Gooch and his throw-down tool which helped improve the solid forward defence that made plenty of appearances this innings. The middle of the bat was often elusive, but Finn played late and, generally, with soft hands. Gooch lives for such success by the batsmen he works with. This will have given him as much pleasure as a Cook or Ian Bell century.

Finn ticked off a host of personal landmarks; highest Test score (for the second time in the game), highest first-class score, maiden Test fifty. The half-century was greeted with a rather apologetic lift of the bat. Across the two innings in this Test he faced more deliveries (243) than he had in his previous 17 Tests. Against South Africa last year he was at No. 11 so his batting has progressed in a short space of time.

Finn has assumed the nightwatchman role from James Anderson, who did the job on 21 occasions. The most recent, and now likely to be last when Finn is alongside him, was against India in Ahmedabad, where he fell for 2 on the second evening before seeing through the overs.

Anderson put in some battling stints - notably against South Africa at Headingley in 2008 when he was roughed up by Dale Steyn - but is not going to be taking the position back any time soon. "It was a good selection," Cook said. "We've always know Steven has a solid defence and he showed that today."

Nightwatchman statistics can be a grey area - for example a couple of times Anderson batted at No. 8 to protect Stuart Broad and Graeme Swann, while Mark Boucher has innings classed as being a nightwatchman - but Finn's effort was acknowledged as the second longest for England after Jack Russell's 304-minute marathon against West Indies at Bridgetown in 1990. Russell's innings was not enough to save the team on that day; Curtly Ambrose blew the lower order away to finish with 8 for 45. No one in the New Zealand attack was capable of that sort of impact. That was not the first time Russell made a name for himself in that position; on Test debut, against Sri Lanka in 1988, he reached 94 before driving a wide delivery to cover.

The last England batsman to have such success in the position also came against New Zealand. Alex Tudor is most often remembered for his unbeaten 99 at Edgbaston in 1999 - the high point of a depressing summer for the home side - and would have reached three figures if not for Graham Thorpe finishing things swiftly.

The University Oval in Dunedin is no stranger to nightwatchman heroics this season and Finn's pales into comparison alongside that of Nick Beard, the Otago bowler, who made 188 in 380 balls and 461 minutes against Auckland last month. Beard, 23, is regarded as more of a bowler who bats - perhaps a Graeme Swann or a Broad - but that remains a considerable achievement.

Not, however, quite as impressive, or famous, as Jason Gillespie who made an unbeaten double hundred against Bangladesh in Chittagong in 2006. It did not do much to prolong Gillespie's career - that was his final Test.

Perhaps, though, one of the better nighwatchman stories involves the former Sussex offspinner, and from 2005 to 2006, MCC president, Robin Marlar. Playing for Rest of England against Surrey in 1955 he was out, stumped, second ball for 6 against Tony Lock. He is believed to have said to his captain: "Told you I wasn't a nightwatchman." That is certainly not what Finn will be telling Cook.

*0800GMT, March 11: The story was update to make mention of Finn's wine