I am Lara Croft

This is what happens when you are cut loose in the Land Rover Heritage Collection, which contains the most significant and best-known vehicles to wear the famous badge of the brand since the 1940s.

You can live your fantasies as a reality behind the wheels of the cars which actually did the job, from one of the very first Land Rovers through to Lara Croft's movie star machine and even an SAS fighting truck which saw active service in the Middle East.

The extra-special Land Rovers are lined up at Eastnor Castle, which has been the test base for the off-road icon brand since the 1960s, as part of a money-cannot-buy driving experience.

The history cars are ready for an hour of action, but only after a hectic half day of the toughest off-road driving I have ever experienced in a group of shiny new Discovery 3 escape machines.

It's the best fun I've had in a mud puddle since I was five, and this giant puddle takes up more than a little of the 5000-acre estate at Eastnor Castle with roads which are always special and sometimes named after members of Britain's royal family. And not because they liked the scenery . . .

It's cool and slightly foggy as we troop out of Eastnor - which was built in the early 1800s despite styling which would be fine for King Arthur - and slide into the seats of the Discovery fleet.

My day gets better, much much better, when a man called Roger Crathorne slides into the back and introduces himself. He is known inside the company as 'Mr Range Rover' and has been a driving force across the Land Rover family for more 40 years since joining the company as an engineering apprentice.

Crathorne was the man who led Land Rover to Eastnor, after a golfing friend suggested it might be a good place to do some testing on the 'upcoming' Range Rover in 1962.

"We've been here ever since. And the conditions are some of the toughest we have found," says Crathorne as we begin the day.

He is proved right within 30 minutes when I get our Discovery lightly bogged. It takes a few goes, but eventually I pull free of the sucking mud which has infested the deep ruts which set out our route.

It's typical of Eastnor, which is tackled with the car's Terrain Assistance four-wheel drive system set to 'mud and ruts', with occasional tweaking of the ride height, the downhill assist and all the other stuff you never worry about in Toorak or Double Bay.

This is serious off-road work and, less than an hour later, it gets much worse. The ruts get deeper, the conditions get even more slimy, and Roger is bounding out of the back seat like a 20-something fun runner - not a 60-something retired executive - to lead the winch and recovery work.

He does it again a little later when an assault on the 'American Dips', dug deep through a stream to impress a group of American dealers, turns into a major recovery job for all of the Discoverys.

"This is what it's all about," he says.

And it is. It is also the proof that a Land Rover in the 21st century is just as capable as the 1940s original which was developed from the wartime Willys Jeep.

After using a Jeep to tackle the famed Rubicon Trail in the USA, where it's all about slow-speed crawling over giant boulders, I am convinced the Eastnor test is much tougher. And I would also give the Discovery a tick ahead of the American off-roaders, although it would be fantastic to put them head-to-head at Eastnor.

After a break for tea and a talk, and more advice from our guides and advisors, we move into muddy ruts which are even more worrying than before and then a final test through obstacles hung over a stream. But the Discoverys wade through the deep sucking muck, and breath cleanly in deep water, as they take us on a tour that includes some incredible British scenery - also used by, whisper it, the SAS for training work - and then rise easily to the creek challenge.

At the end they are as dirty as any four-wheel drives I have seen, with mud caked over almost every surface, yet they have been light and easy and luxurious to drive. Particularly with Roger to do the heavy lifting on the winch work.

It's already been a memorable day, but after a barbecue lunch beside the Eastnor lake, it's time for the heritage cars.

I cannot help myself as I jump straight into the Lara Croft-mobile. This is the very same vehicle driven by Angelina Jolie, down to the rumbling V8 exhaust and a body tweaked with all sorts of adventure gear. It's a fun drive and a smile-a-mile experience, even if the movie makers insisted on an automatic gearbox for their star . . .

The Judge Dredd machine is a disappointment after the Croft car, and just getting into the driving seat is a snake-and-squeeze test. The body might be fantastically futuristic, but the cabin is straight from the 1940s.

And so is one of the very first Land Rovers. I find it easy to drive, and much more luxurious than an original Jeep, but you have to concentrate on a low-powered engine and a difficult gearbox and brakes which need planning.

"I think more people should drive cars like this. They would learn what motoring is really about," says Roger, who is again along for the ride.

I take a lap in the SAS machine and wonder what stories it could tell, clamber into an early Land Rover truck, and then fall deeply into a Crathorne trap.

"Why don't you have a drive of this? We'll see what your muscles are like," he says, pointing to a machine with tracks instead of wheels for a polar expedition.

It goes well at first but when I have to turn . . . it is impossible. There is no give in the tracks and it takes be about 57 goes - well, maybe not that many - to make a simple 90-degree turn.

"It's a lot easier on the grass, isn't it?," Roger says with one of those Yoda-style smiles.

And that is typical of everything about the day with Land Rover. What looks easy is very tough, but incredibly educational and enlightening.

It's a history lesson in a day, as well as a course in engineering and driving, and chance to see what four-wheel-drive development is really all about.

We are about to see the 2010 models of the Range Rover, Range Rover Sport and Discovery 4, which will be shiny and new and luxurious and ideal for cashed-up Australian families.

But they can also do the sort of work which has made Land Rover so successful for more than 60 years.

At the end of the day, I find myself on top of one of the towering battlements of Eastnor Castle. I am strapped to the third-longest flying fox in Europe, nearly 10 stories above the ground and facing a 300-metre run out across an icy-cold lake.

How did I get here? Why? These are two of the questions which spark through my head as I prepare to throw myself off a perfectly good castle to overcome a lifelong fear of heights.

Eventually, after three failed attempts, I slide over the edge and scream like a child. Lara Croft? Maybe not today after all

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