It matters not whether it is Catterick on a cloudy Friday afternoon with a modest card attracting a crowd to match or sun-drenched Epsom on Derby Day drawing Her Majesty and perhaps 100,000 others, some in black toppers, others in faded denims; it is the uncertainty which provides racing's spark.

Doubt, hesitation, perhaps even a little fear, all played their part in the finale to a fascinating build-up which deserved and received confirmation that in racing you just never know.

Take two horses: River Proud and New Approach. The former was added to the Derby field as an afterthought by their owners, largely on the advice of trainer Paul Cole.

To take such a course demands more than a little courage – the fee to supplement a horse in the Derby is £75,000. For that money you expect at least to run but connections of River Proud had to withdraw their horse on the day of the race after he had been found to be lame on Friday.

New Approach, last year's champion two-year-old, was second in both the 2,000 Guineas at Newmarket and the Irish equivalent but his trainer Jim Bolger had told the world several times his colt would not be taking his place at Epsom, not because of any worries over the horse's ability to take on the extra half mile of the major Classic but because he favoured a longer break before going for the Irish Derby at the Curragh.

It was the sight of New Approach bucking and squealing a day or so after running in Ireland that he decided to advise the colt's owner to take on the Derby and then, because of New Approach's quirky temperament, which forces the yard to have him "ponied" to the start by stable-mate Metamorphosis, he had to come to an agreement with the Epsom authorities to break with the traditional routine on the biggest day of all.

Bolger, jockey Kevin Manning and owner Princess Haya of Jordan could not know how their charge would react to the madding crowds of Epsom or the switchback course; uncertainty was never far from their shoulder. But they also knew that, given luck in running, they had a great chance of pulling off a famous victory.

Even two furlongs from the winning post there must have been doubts as Manning appeared to have nowhere to go and Tartan Bearer, the winner of last month's Dante Stakes at York, was unleashed by Ryan Moore on what looked certain to be a winning surge down the middle of the track.

Manning had to gamble by switching inside, heading for the rail. He found the gaps at the right time, fortune was on his side and New Approach had the speed to overhaul Tartan Bearer in a gripping finish, the pair pulling well clear of the remainder and the second fighting back with rare courage to close the gap in the last few strides.

Did Tartan Bearer get to the front too soon? We will never know and this morning it does not matter; what we do know is that New Approach was a worthy winner and proof once again that in racing the only certainty is uncertainty.