A hero to the ancient Britons. However, a rebellion that was brutally suppressed by a token Roman force. The battle of Watling Street ended the revolt of Boudicca of the Iceni and other Britons in the recently conquered province of Roman Britain.

A Brief Background.
Britain had been conquered by the Romans in 43CE. The various tribes were forcefully annexed or voluntarily cooperated with the Romans. The Iceni, based in modern day Norfolk, allied with the Romans. After the death of their king, Prasutagas who bequeathed his lands to his family and Rome, the Romans annexed the full measure of the land. To add salt into the wounds, Boudicca, Queen of the Iceni was flogged and her daughters raped, which lit the fire of resistance.

With the Roman Governor Paulinus campaigning in what is now Wales, Boudicca roused the Iceni and their neighbours into a revolt. They sacked Camulodunum (modern day Colchester) which was a veterans Roman colony, a key town in their colonization efforts. Those who could not escape were slaughtered. A legion, IX Hispania confronted Boudicca’s forces but was destroyed.
Enter the Governor.
Paulinus on hearing reports of the revolt made for Londonium (London) and reached before the Rebels. He evacuated the town having deemed his force (which with his initial legion, the XIV Gemina and auxiliaries and other detachments numbered 10,000, while a legion based in Southwest England, II Augusta refused to join). Those who remained, were slaughtered when the Rebel army arrived. The same happened to the Roman city of Verulamium, with Paulinus evacuating those who came, whilst those who remained were slaughtered when the Rebels arrived.
It’s estimated over 80,000 Roman civilians (including some of the military forces in Britain) were killed. The three major cities of Roman Britain were sacked. For a new province that’s being colonized, it was a big blow.

Boudicca’s army was in hot pursuit of Paulinus’s force. Realizing a battle was inevitable, he sent the civilians away on a north western route to Wales where a new settlement could be founded.
By the time the two armies would collide, Boudicca’s coalition had swelled with over 100,000 warriors (men and women). Despite them being disarmed in the previous years by the Romans, they had equipped themselves with Roman weaponry from the destroyed cities. They were fairly well armed but there was one significant advantage the Romans possessed: Experience.
Roman soldiers by this time were professional troops, including their auxiliaries. Having just conquered Britain and still fighting resistance in the northern half of the country, they were experienced in warfare and a disciplined force.
The Battle.
With an obvious understanding he was greatly outnumbered, battlefield choice played a big role and Paulinus chose his site well. He found an area with thick forests and gorges around him. This protected his flanks and rear. The entrance to his position had a narrow chokepoint which would funnel the Britons into manageable numbers.
For his pre-battle speech, Paulinus was brief, as if he did not expect him or his men to survive the day. According to Tactius, the speech made was:
Ignore the racket made by these savages. There are more women than men in their ranks. They are not soldiers—they’re not even properly equipped. We’ve beaten them before and when they see our weapons and feel our spirit, they’ll crack. Stick together. Throw the javelins, then push forward: knock them down with your shields and finish them off with your swords. Forget about plunder. Just win and you’ll have everything – Paulinus
The Britons had come with war wagons from which non-combatants were to watch, and prevent any chance of a Roman break out. Charging against the Romans, the battlefield started to influence the fight. The chokepoint before the Roman lines funnelled the Britons. The Romans, standard to any battle threw their javelins that destroyed the momentum of the Britons first line of charging troops.
Paulinus deployed his men into 3 wedge formations and shocked the Britons by charging against them. The Wedge allowed them to fight in multiple directions simultaneously. In addition, the Roman Legionary was equipped for brutal close quarter fighting .They weren’t overwhelmed and the Britons were gradually pushed back.
By the end of the day, the battle moved to a stale mate. The Britons tried to retreat but their own wagon crescent blocked their escape. The Romans capitalized on this. In the confusion and subsequent rout, the Legionaries showed no mercy. It is estimated at just a cost of 400 Roman Soldiers, over 80,000 Britons were killed in the massacre.
It might have been resounding military success but including the town massacres, it was a brutal affair for both sides. The Roman occupation of Britain took a massive blow, but many Britons were also massacred.
Back in Rome, Emperor Nero nearly contemplated abandoning the island on hearing about the revolt. However those plans would be shelved on hearing the rapid end. Paulinus was replaced as governor of Britain for fear this policies might instigate more unrest. A more conciliatory, moderate governor was appointed in his stead.
Most of Britain would remain under Roman Occupation until it was abandoned in the 5th century.

On a side note, the Prefect of the II Augusta, who did not allow his men to join the fight committed suicide on hearing the news of victory.