Reins of terror

National Hunt jockeys are crazy, according to horse trainer Pat Murphy. And when Mark MacKenzie saddled up on one of Murphy's frisky 'equine athletes', he discovered why - very swiftly indeed

'If you come with me, I'll show you to your conveyance." Pat Murphy leads me through his Berkshire racing yard and stops outside a stable door. "Have you ever ridden a racehorse before?" The 44-year-old Irish trainer grins as I shake my head, and steps into the dimly lit stable to grab a set of reins. Given the premiums for racehorse insurance, I'm expecting him to emerge with Steptoe's drayhorse, but out steps a racehorse. A real racehorse. One of Pat's "equine athletes", half a ton of ripped racing muscle. Linford Christie with four legs instead of two. Muharib Lady.

Pat gives me a traditional jockey's leg-up, throwing my 11 stones into the saddle, and reminds me to "stay between the tail and the ears". Despite my rudimentary riding skills, I've always prided myself on being able to calm a horse through the ability to exude total confidence. A half-baked nonsense of a theory that is about to be tried, tested and shovelled up with the rest of the horse shit.

Two of Pat's stable lads, Kieran and Jo, saddle up and tuck in behind me, forming a "string". As we head to the nearby gallops to put the horses through their daily workout, I am about to get a unique view of what is, football aside, Britain's most popular winter sport by miles. National Hunt racing.

To anyone newly arrived from Mars, National Hunt racing takes its name from a centuries-old association with fox hunting, and is horse racing over jumps. Its tests range from two-mile hurdle races – fast, flat jumping over low barriers – to the epic, four-and-half-mile Grand National steeplechase and the mountainous obstacles of The Chair and Becher's Brook. Which is why, in contrast to their Flat-racing counterparts, jump horses are bred as much for their robust-ness as their speed.

The wet conditions mean today we will be working the horses on the all-weather track. As Pat drives ahead to the top of the gallop, Jo and Kieran steer me through a gate and on to the wood-chip surface. And then everything changes. Kieran's horse starts violently tossing her head and he urges me to shorten my own reins as beneath me, Muharib Lady begins to bunch and tense up. Kieran's horse drops to her hindquarters before firing herself forward. After a few lunging strides we're cantering, and Muharib Lady floats over the track, eating up the ground. I can hear the horse working, but her running action is so smooth I can barely feel it. Kieran shouts to tuck in behind him but Muharib Lady is desperate to lead. My lack of riding fitness means I'm powerless to stop her, and at the top of the gallop, Pat brings her to a halt with quiet "Whoa girl".

This is clearly a man who knows horses. The star of Pat's East Garston yard is Supreme Glory, recent winner of the Welsh National and among the favourites for the Grand National on 6 April. Until last summer, Pat also had custody of Shooting Light, a hot tip for Thursday's Tote Gold Cup at the Cheltenham Festival.

Like all élite athletes, a racehorse's regime is geared toward peaking for the big races in the season, and Kieran and Jo are working their horses at only half and three-parts speed. "Racehorses are naturally competitive and are often harder on themselves than you would like them to be," explains Pat. "You need to hold something back in training because you don't win any prizes for finishing first on the gallops at home."

Back at the yard, Pat attempts to impart years of family horse knowledge in the time it takes to drink a cup of tea. An exponent of "loose schooling", he treats horses as individuals, and cites Supreme Glory as an example. "When the horse came from Ireland, he had a lot of potential, but I could see he wouldn't stand a lot of racing, mentally rather than physically. He's only had 16 races in his life and he's nine years old, that's very few miles on the clock. It's vital that you don't break a horse's heart by continually racing him against superior animals."

National Hunt racing in Britain is governed by the Jockey Club. Once a horse has run three times it is given a weekly handicap rating in line with its performance. Handicap marks are posted to trainers, and races are rated to ensure horses of equal ability run against one another.

A key part of the trainer's art is to try to cheat the handicapper, not showing his hand at a minor meeting if he is saving a potentially explosive horse for a big race.

And then there are the jockeys. Pat explains that while the days of "binge dieting" to make race weight have long passed, jockeys still need to be "touched by a certain sort of madness". "Take our champion jockey, Tony McCoy. He goes out six times a day, firing horses over jumps at 35mph. The faster the better. Now that can't be normal."

While the rewards for successful jockeys and trainers can be as much as 10 per cent of the winning purse – prize-money for the Grand National stands at £500,000 – the penalties for taking a tumble are harsh. Pat's brothers, well-known former jockeys Declan and Eamon Murphy, both retired through injury. Declan suffered a kick to the temple that briefly rendered him clinically dead, while Eamon goes about his daily business without the use of his spleen.

All of which Pat has neglected to mention as we turn for our second run up the gallop. Hitting the front once again, Muharib Lady decides she has kept her mischief bottled for long enough. Running alongside the all-weather track is a grass gallop, strictly out of bounds for anything other than flat-out workouts before big races. Spotting the metal dividing gate has been left ajar, Muharib Lady veers sharply left and makes for the gap. There is an almighty clang as my right stirrup whacks the gate, and suddenly we're clear and Muharib Lady is flying.

On Pat's advice I use the reins as brakes but, convinced the reins are in fact the clutch, Muharib Lady takes it as a cue to ratchet up the gears. At top speed a racehorse can expect to touch 40mph. I've no idea if we're anywhere near that, but the rush is absolutely incredible.

At the top of the gallop, a bemused Pat brings Muharib Lady to a halt. He informs me I have been officially "run away with" and asks if I enjoyed the ride. Only in a "most exhilarating 30 seconds of a lifetime" sort of a way.

National Hunt racing's Cheltenham Festival runs from Tuesday this week to Gold Cup Day on Thursday. The Martell Grand National is at Aintree on 6 April. For details of riding lessons, call the British Horse Society on 0870 120 2244 or visit www.bhs.org.uk

Do

Stay between the tail and the ears: the optimum position to enjoy the ride.

Bring a Polo mint: racehorses are notoriously fickle and open to bribery.

Stand at the front of the horse: getting kicked hurts.

Don't

Ride with long reins: lack of control could lead to a very long ride.

Fall off: it's a long way down once you're airborne.

Forget your goggles: seeing through mud and rain at 40mph is tricky.

Overfacing Damaging a horse's spirit by training it over obstacles that are too large.

Toe board Guideline board telling a horse when to jump.

Belly of the fence Distance travelled between toe board and top of fence

Slogging the guts Over-racing a horse in wet conditions.

Crib biter Keeping a racehorse mentally alert is key. Biting the stable door or crib indicates a poorly motivated animal.