Surrey 300 for 5 (Sangakkara 166, Wilson 48, Foakes 42) beat Nottinghamshire 296 for 7 (Smith 124, Patel 51, Mullaney 42*) by four runs

A wonderful Royal London Cup semi-final which could have fallen either way bestowed its gifts upon Surrey by four runs when Tom Curran held his nerve and prevented Steven Mullaney hitting the last ball for what would have been a match-winning six for Nottinghamshire.

So it is Surrey, a coming force again in the county game, who have the chance to follow promotion from Division Two of the LV= County Championship with a one-day trophy when they meet Gloucestershire at Lord's on September 19. It is Nottinghamshire who despite their midsummer rally once again fail to prove their pedigree with a trophy. On such small margins are conclusions drawn.

The stark contrast between the game's two dominant batsmen - both of whom made hundreds - was just one facet of a match that showcased the county game at its finest and which questioned the sense of staging this semi-final as a Monday day game with the schools beginning a new term. One batsman is famous, even to those who don't follow the game; one may not be known, even to those who do.

For Surrey, there was Kumar Sangakkara, a legend of the game, extolled to the heavens during his several international retirements, a man who could become a Sri Lankan high commissioner, perhaps in London, if he wanted it badly enough. For Nottinghamshire, there was Greg Smith, loaned out to Leicestershire earlier this season, playing his first Royal London Cup game of the season, just another Smith to some, a jobbing county pro taking on the best, proving his worth, so close to glory.

Sangakkara's unbeaten 166 fell only three runs short of his record one-day score made against South Africa in Colombo two years ago. He has been chaired from outfields, chased by photographers, and has been the subject of endless appreciations. Smith's response - 124 from 134 balls - was his only notable performance of a summer when appreciation has been in short supply. He only played because Alex Hales and James Taylor were away with England. But how pluckily and robustly he responded.

"We were nervous," said Surrey's captain Gareth Batty. "Notts are a very good team. Kumar is the best player in the world still. What is a disappointment for world cricket is the best news possible for Surrey."

Sangakkara's will to win remains as strong as ever. He carried Surrey to a Lord's final with an indomitable innings of character and know-how, an innings which left him exhausted but ultimately triumphant. Michael Klinger saw off Yorkshire in the first semi with a hundred, now Sangakkara - just - did the same: two fine overseas stars earning their corn.

Presented with a dry, benign pitch, he took the onus on himself to deliver. His first hundred including only six fours and a six as he worked deliveries towards a 90-yard long boundary and steeled himself for endless to-ing-and-froing. Then as responsibility also rested with him to lift the scoring rate, he stepped it up so successfully alongside Gary Wilson that 109 came off the final 10 overs, such acceleration harder now with five fielders allowed out in the deep, and he dropped to his knees with fatigue more than once, staring blankly into the distance and perhaps wondering what on earth he was putting his body through, at 37.

Those thoughts were doubtless never stronger than as early as the fifth over when he took a jittery single off Harry Gurney to get off the mark and, diving to make his ground, demolished the stumps. They rarely looked in danger again as he chipped the ball into the gaps with precision, crucially taking 21 off the penultimate over, from Gurney, with a series of scoops, paddles and reverse paddles, before Jake Ball defeated a shot of similar intent in the last over.

Surrey had other heroes. Watching the young Curran brothers for the first time is an intriguing sight. Sam is only 17, a wisp of a lad with a brisk, whippersnapper run-up, trendy haircut and an ability to swing his left-arm pace, as both Riki Wessels and Brendan Taylor discovered in the second and third balls of his first over.

Tom, a comparative veteran at 20, sports a bob; his right-arm is delivered from a more loping run and he looks more of a workhorse. For Tom to cope with the pressure of such a run chase was admirable enough; for Sam to do likewise, as he delayed his return to A levels at Wellington College for a day, was utterly remarkable. Add Yorkshire's Matthew Fisher and county cricket has witnessed the arrival of two 17-year-olds this season of great promise.

Smith came in for Sam Curran's hat-trick ball, soon to become 17 for 3 when Michael Lumb fended at a wide one. Smith's response was admirable. Nottinghamshire said they had a dangerous one-day strokemaker when they signed him and he proved as much. If he had made a million, with Hales and Taylor to return at Lord's, he would not have been sure of a spot in the final

At first, he was accompanied by Samit Patel, the size of the task encapsulated by his characteristic haunted look. The wider his eyes, the tougher the run chase. There was no doubting the quality of his half-century - he remains one of the best players of spin in the country - but, as so often with Samit, he provided the odd comic moment.

In the wake of Sangakarra's guelling innings, he contrived to be treated for cramp himself, having made 6 from 12 balls. "I know how you feel," one could imagine him saying to Sanga. His innings ended when he pulled a long hop from Zafar Ansari to deep square.

Eighty-four off nine overs with Dan Christian in, and a clubbed half-century to his credit, was very much on for Nottinghamshire. After a chat with Sangakkara, Batty turned to Aneesh Kapil, his sixth bowler, three overs delivered for 23, a fixture in the 2nd XI. It seemed a left-field call, but Christian carved his third ball to one of three players around square on the offside.

Notts' fifth-wicket pair had luck on their side. Smith and Steven Mullaney found themselves together at the wicketkeeper's end at one stage, but Surrey failed to take advantage. Lofted shots dropped repeatedly over despairing hands. Tom Curran showed a cooler head when he ran out Smith off his own bowling with 27 needed off 17 balls, a little run followed by a little throw.

Then, to cap it all, Jade Dernbach bowled the bravest delivery of the season, a daringly slow back-of-the-hand yorker which struck the base of Chris Read's middle stump. More than any other English cricketer, with the possible exception of Kevin Pietersen (an altogether different story), he is vilified on social media. He deserved recognition for that, especially as Batty revealed the pain he was under.

"He epitomises Surrey - he bowled those late overs with a torn calf," said Batty. Dernbach left Tom Curran to defend 14 off the last over - and with his last ball - full and wide outside off stump, guarding the short legside boundary - he accepted the offer with aplomb.