Some moments in history are pivotal; crunch points upon which the futures of millions of people are decided.

Yet as the years pass many become forgotten. So you might not be aware of one such event which took place right here in the county.

It saw tens of thousands of men locked in a brutal three-day battle and had the outcome been reversed, there’s every chance the Britain we know today would be unrecognisable.

Now a leading historian from Mereworth, near Maidstone, is shining a light on what has become known as the Battle of the Medway.

“There are two sliding door moments in the history of Roman Britain,” explains Dr Simon Elliott whose latest book is called Great Battles of the Early Roman Empire, “and one is the Medway crossing battle.

“If the Romans had lost, I think they would have gone home and licked their wounds and not bothered invading Britain again. That would have been it.”

The second, by the way, was Boudica’s famed attempt to defeat the Romans as they established themselves as the island’s rulers.

So where did this battle – which would cost the lives of thousands – take place and why was it so significant?

First, a little context.

The Romans, under Caesar, had landed in Britain twice – in BC54 and 55 – thought to have come ashore at Pegwell Bay, in Thanet – but despite some success, had withdrawn to mainland Europe. But when Claudius became emperor, he became determined to conquer in order to secure the political plaudits he was in need of back in Rome by extending the empire.

So in AD43 he sailed up to 40,000 legionnaires to Kent – arriving along what was then a major waterway, the Wantsum Channel, which separated Thanet with the rest of the county, and the coastline down to Sandwich.

“You need to think of their arrival as a bit like D-Day,” says the historian who has fronted a number of TV history shows, “it would have been vast and along a long stretch of the east coast.”

It was a significant show of force and one which knew failure was not an option. It also knew failure equated to certain death.

“When Caesar came to Britain he didn't come to stay,” says Dr Elliott. “It was like an army reconnaissance or PR exercise because he was in the middle of conquering Gaul.

“But that's what put Britain on the Roman map. Basically, the Romans thought of Britain in terms of the things they could get from its raw materials; precious metals, tin, lead and iron. Britain was even famous for exporting mastiffs, hunting dogs, and woollen goods.

“You have to remember the Roman Empire is a Mediterranean empire. We in the northwest of Europe, Gaul, the Rhineland and Britain, were, to use a Game of Throne analogy, north of the wall. It's across the wall to the Badlands because you know the Romans haven't been there before until Caesar.

“Britain was always a marginal province. I always call it the Wild West of the empire. But Claudius will ill-favoured and he needed a big win – conquering Britain was the way to do that.”

Having landed and constructed a significant for at Richborough, his legions – lead by his general, Aulus Plautius – headed inland.

As the troops set off to conquer the nation, Dr Elliott believes they followed the old Pilgrim’s Way route to the south of the North Downs – a route which would have allowed them to benefit from the maximum amount of daylight each day.

They encountered two significant confrontations with native tribes as they made their way into northern Kent – emerging triumphant in both. But a far sterner test was around the corner.

Explains Dr Elliott in his new book:”Plautius quickly reached Bluebell Hill overlooking the Medway Gap where the River Medway cuts through the North Downs.

“There, instead of continuing along the route of the Pilgrim’s Way as it turned north before crossing the winding river at Cuxton, he instead headed directly westwards, aiming to cross at one of the then well-known fording points on the Medway.

“Here, there is now some real debate over the actual site of the fords he targeted, this being very important given his choice led directly to the battle taking place there.”

Previous theories have pointed to him heading for the twin fords where today Snodland and Aylesford are located. But Dr Elliott believes this may not be correct, given the marshy conditions – far from ideal in conducting a brutal battle on foreign soil.

He instead suggests Roman marching-camp sites, potentially recently uncovered at West Farleigh and Mereworth, point to a different site.

He explains: “If they do prove to date to the AD43 campaign, this would then see Plautius’ forced crossing of the Medway moved upriver to a broad front west of Maidstone along the river at East Farleigh, Barming and Teston, where the Medway has historically been fordable and where modern bridges are located today.

“Here, the river valley is shallow with gentle slopes leading down to the Medway from the high ground above where the West Farleigh marching-camp site is located, with no marshland to impede a gentle approach to the fords along the river. This would be a far more agreeable battlespace for Plautius to operate in.”

But as the legions attempted to cross the river they were met with fierce resistance from combined forces of native tribes determined to repel the invaders.

They were armed with slingshots – which may not sound much but could do considerable damage.

Dr Elliott explains: “The Britons were famous for using slings, not bows. And these were a really deadly weapon. If it’s firing a hard stone or lead shot it would be like a low velocity pistol bullet. It didn’t need to penetrate your arm or helmet to actually damage you. You get a good sling hitting you on the head with a lead shot, it would certainly incapacitate you and it might still kill you.

“You might break ribs or an arm if it hits you on the torso and the the Britons were really skillful with them.”

It seems bizarre, given the scale of the battle and its ferocity that no site has ever been confirmed – primarily due to a lack of contemporary reports at the time.

The normal way in which Roman routes across the nation have been chartered is through the position of its marching-camps.

Thrown up each night, they involved ditches being built to protect the legionnaires, with the stakes they carried creating an inner line of protection against overnight attacks. Due to the soil conditions, the traces of many in the likes of northern Britain and Wales can still be seen. Then, as Dr Elliott puts it, it’s a case of “joining the dots” to chart the route taken. It is more tricky in the south, however, due to our geology.

But the recent discoveries of possible sites in Kent could provide vital clues as to the spot this bloody battle was waged.

Eventually victorious, it was a key moment for the Roman forces.

Shortly afterwards, Roman emperor Claudius arrived in Britain bringing reinforcements – among which were elephants; the sight of which must have terrified the natives.

The rest, as they say, is history.

Dr Simon Elliott’s book, Great Battles of the Early Roman Empire, which describes eight of the greatest, most decisive of the Roman Empire of the first to third centuries, is available now and published through Pen and Sword Books.