The men's national championship road race goes over one of South Wales' most feared climbs - the Iron Mountain. Or, as it's better known in the cycling world, the Tumble.

Cycling Weekly came down to South Wales today for the weekend of racing and decided to take a quick look at what's in store for the men's championships. (The women's and junior races use a different circuit that doesn't feature the Tumble.) The climb starts in the town of Llanfoist and climbs to over 400 metres above sea level in just over three miles.

The very bottom is gentle enough, but it doesn't take long before it ramps up and around the first hairpin. After that it's a long straight under the trees that becomes quite a drag. Round the second hairpin and there's another long straight that looks as if it gets steeper in the distance.

At the end of that straight it's over a cattle grid and in to classic Welsh mountain scenery - with sheep and mist thrown in for good measure.

It's this top section that really starts to bite as it winds it's way around, hugging the side of the mountain.

Unfortunately for us the top of the climb was shrouded in mist, so we didn't know we were at the top until we arrived there - and then there was no view to enjoy. Instead it was on with the rain capes and gilets and off down the other side towards Blaenavon. 

The Tumble is unlikely to trouble any of the continental pros returning this weekend, but it's tough enough to split the 191 rider field that will tackle it. Any splits that do open up are likely to stick as the approximately 20 mile circuit has a sting in the tail.

Just before the riders hit the centre of Blaenavon they're sent right and back up and over a smaller climb. It doesn't compare to the Tumble, but the undulating road will catch some riders out, especially if there's a wind blowing.

The riders that do get over this section in front are likely to be the ones battling it out on the shorter finishing circuit around Abergavenny as the descent towards Brynmawr is followed by a fast section of main road all the way back.

My tip for the podium? I'm going to say Millar, Hunt and Russell Downing. Most of the British pros are exhausted after the Tour Series and Cavendish wont be able to move without 20 riders jumping after him. 

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National Championships 2009: The big preview