Adam Hart-Davis investigates the extraordinary innovations that the legions brought:

WE should not be surprised that native Britons succumbed to the Roman military invasion and were later seduced by their way of life: the Romans were way ahead of their time.

The Romans invaded Britain in the spring of ad 43, landing at Richborough in Kent and marching rapidly to take the stronghold at what is now Colchester. The invasion was quickly successful, partly because the Roman army was highly disciplined and had an effective logistical infrastructure, but also because they could draw on technology that was hundreds of years ahead of what was available in Britain.

They introduced to this country not only straight roads, elegant baths and flushing lavatories, but also rectangular houses, apples, pears, carrots, turnips, three-course meals and even hamburgers. The bars in Londinium and other Roman towns sold not only hot breads, pastries and pies, but also fried patties of ground beef, salt, pine kernels and a slurp of wine, eaten with bread - clearly a precursor of the Big Mac.

Even today we drive on a number of Roman roads - the A68 near Corbridge, Northumberland, the A2 in Kent, and so on - that were built to get troops quickly around the country. They have been resurfaced many times since the legions last marched on them, but tens of miles of foundations and agger - the bank on which the road was laid - have survived 2,000 years of wear and tear - a remarkable fact considering that they now carry vehicles many times heavier than anything the Romans rolled over them.

Better roads were not built until Thomas Telford and John Loudon MacAdam came along in the early 19th century, so you could argue that the Roman engineers were 1,800 years ahead of their time.

The most obvious thing about Roman roads is that they are straight, but making a straight road is not difficult; what really impresses me is their surveying.

When they decided to build a road from London to Chichester, the Romans set off in exactly the right direction, even though they apparently did not use map or compass. Instead, they used a lovely piece of low technology called the groma, a stake stuck in the ground with a horizontal frame in the shape of a cross on top and plumb-lines hung from each arm. This allowed the surveyor to adjust a beacon until it was precisely in line with beacons on either side. By doing this all along the prospective road, they were able to mark out the exact line they needed.

Once they had built their road network, the Romans used it as a sort of grid to help calculate the size of farms and other land holdings, in order to levy appropriate taxes. To measure the distances from A to B, they first used pacers, soldiers trained to march with a standard pace and to count their paces. The standard pace - left, right - was about 4ft or 1.2 metres, and the Roman mile was mille passuum (a thousand paces) which is about 0.8 miles or 1.2 km. They erected massive milestones to record the intervals.

Later they built odometers, described by Vitruvius, in order to measure the distances automatically and more precisely. Rather than just being a dial on the dashboard, the Roman odometer was a chariot in its own right, with wheels 4ft in diameter that turned exactly 400 times in one mile. Each revolution, a pin on the axle engaged with a giant 400-tooth cogwheel, therefore turning it once in exactly one mile. At this point another gear meshed, and caused a pebble (called a calculus) to drop into a box. So at the end of a journey, the number of miles travelled was given directly by the number of pebbles in the box.

This seems to have been rather more effective than the device Sir Joseph Banks fitted to the carriage he designed some 1,700 years later, as described by one of his friends: "The vehicle boasted a hippopedometer by which a traveller might ascertain the precise rate at which he was going.

"This broke, in the first 10 miles of our journey: whereat the philosopher to whom it belonged was the only person who lost his philosophy."

The Romans also had an answer to flooding in mines, which has been a problem ever since miners had enough technology to tunnel deep into the earth. In 1712, Thomas Newcomen, a Dartmouth ironmonger, built a large steam engine to pump the water from a coal mine in the West Midlands. This was arguably the greatest ever step forward in technology, for it provided portable power for the first time, and hundreds of Newcomen engines were built in the next 50 years before James Watt boosted their efficiency and versatility.

But the Romans had been pumping water out of mines hundreds of years earlier. In the gold mines at Dolaucothi in south-west Wales they installed water wheels some four metres in diameter; each was powered by a slave walking up the outside, like a treadmill, and each minute raised some 80 litres of water - half a bathful - about three metres. A stack of such wheels, one above the other, pumped the water clear out of the mine, from deep underground. As I discovered, driving one of these water-wheels was both exhilarating and exhausting.

The Roman army needed clever signalling systems, for example to get messages back from the front line at Hadrian's Wall to Vindolanda and other forts a few miles south.

They had at least two simple code systems using flags by day and flaming torches by night, and these were probably as good as the celebrated telegraph invented by the Frenchman Claude Chappe in the 1790s.

Some of the technological ideas that the Romans dreamed up were truly extraordinary.

Towards the end of the fourth century ad, an unknown writer, alarmed that the mighty empire seemed to be crumbling, wrote a long letter to the emperors (there were two at the time) suggesting a number of devices that he thought would help revival. Some of these suggestions were fairly sensible - methods of saving money on the army, and a huge ox-powered paddle-ship that he claimed would be the fastest thing on the sea.

However, he went over the top when he described his idea of a portable inflatable bridge, which he said no modern army should be without in case they had to get over unexpected rivers or swamps.

Animal skins, carried on carts, were to be inflated with bellows and lashed together to create a sort of giant lilo on which the soldiers could cross dry-shod.

We decided to build one of these inflatable bridges, though instead of animal skins we used floppy plastic bottles, and we lashed them together with gaffer tape. After many hours of struggling, I was just able to walk on the bridge across a modest river.

I could hardly imagine an entire legion marching across with all their armour. However, the idea was not so daft, for today the fire brigade use just such an inflatable bridge to rescue people who have fallen through the ice, and to get across swampy ground, so perhaps this dreaming Roman really was 1,600 years ahead of his time.

When they first arrived, weapons and armour provided the leading edge of the new technology. Roman metal-workers were highly skilled; their swords were probably harder and sharper than those of the defending Britons, and their throwing spears were made with soft metal shafts that bent on impact, so preventing the enemy throwing them back.

The Romans had several artillery weapons, including the stone-throwing onager, named after the wild ass, perhaps because of its kick, and the fearsome ballista, like a heavy crossbow on a stand. This could shoot a 500g iron-tipped bolt 200 or 300 metres with deadly accuracy.

There is even a description of a repeating ballista. We built one of these and found that it could fire a bolt every five seconds, which would have been devastating to an enemy armed with simple bows and arrows.

The weapon may never have been developed because it was too precise, and would have killed the same man several times, but the technique has been revived in machines that throw tennis and cricket balls at brave defenders, with much the same lethal velocity of 50 metres per second.

However, today's manufacturers have cunningly designed the machines so that the balls swerve, for like politicians, they make every delivery with spin.

From the Daily Telegraph