At the Battle of Watling Street, why didn't Boudica's British try to outflank the Romans?

They tried to coax them from their strong position. The charioteers probably initially swept parallel to the Roman position throwing spears and attempting to taunt them into pursuit. But the Romans were having none of it, and remained steadfast. The Britons could have taunted them all day long and they wouldn't have budged.

Tiring of this, and supremely confident of their enormous numerical advantage, they charged. And who could blame them? The Romans themselves must have had some serious reservations about the situation, even with Paulinus' attempt to calm their nerves. I doubt that Boudicca and many, if not most, of the Britons had any real knowledge of the physics of crowd control in battle as the Romans did. Some of her lieutenants may have tried to dissuade her, but their faith in their numbers and bloodlust prevailed.

The Britons had total victory before them. They completely destroyed the Roman capitol, Londinium, and Verulanium, in addition to annihilating an entire legion sent from Lincoln to relieve Camulodunum. They must have had little doubt that the gods favored them, and would grant them victory.

well the Celts were a rabble basically they were not a trained army like the Romans they travelled on mass had carts with the family aboard travelling with them Tacitus the Roman writer said there was 150,000 British we can include women and children so it begins to look more realistic obviously the men would charge at the Romans but their bags and baggage blocked their retreat as you say the bottle neck did for them and the famous saw formation of the Romans and shields funnelled the leaders into the killing zone and the ones behind got mowed down by their own fallen and the Romans advancing in formation they all got trapped by their carts and families behind them a total massacre 10,000 Romans all together two armies defeated 150,000 the story went back to Rome pretty impressive by any standards doubt the yanks could beat that a joke of course 10 GIs and 10 modern repeaters could probably do it

Nobody knows where the battle took place, or the (Briton's) conditions and reasons for the action taking place where it did.

And you are asking a bunch of armchair generals (and I see Fishface has come up with his/her own brand of idiocy) to speculate without details.

Although you are prepared to, most intelligent people might think that such speculation was futile.

The Roman flanks were secure the mass attack used by the tribes does not work with a forest in the way.

She was not a General and up against the best army in the world at that time. As she could not break the

Roman line, she was never going to win.

Its not that simple. The Romans were well organized and well trained fighting men. They were well aware of the onslaught outnumbering them. So what they did is form a cordon of men representing a diamond shape. So you have the first diamond shape connected to the next one. So every single man was shoulder to shoulder with shield in front of him in tight formation. They were ordered to keep stabbing from behind their shields and at the same time push forward no matter what the odds were against. As the body count mounted (and then some) the Romans would step over the dead bodies but keep pushing forward. There is 15,000 Romans doing this against a hoard of some 170,000 untrained (fighting) civilians charging against them. To offset the possible flank scenario where-by the British try and get to the rear, the Romans had the cavalry and scouts watching for such a possibility, so there was no way they would be taken by surprise in this way. With the Romans pushing hard forward - continually stabbing at any body part they could see beside their shields, the British panicked and withdrew. Whilst the British were withdrawing the Roman Cavalry charged from behind the line from both sides to follow though on the fleeing Britons. The Romans now had the Britons dispersed and as a consequence they were slaughtered. After that the Romans back tracked to catch up with the women and children and non fighting men behind the lines on their side and slaughtered every single one of them.

If you add it all up, the Roman army was well prepared, equipped and organized to deal with this threat.

she was probably just a dumb, arrogant Celt...the Celts were noted by the Romans to be "not very smart' (more like minds of children vs. grownups in a battle someone wrote they were easily roused up to charge and had not hardly any strategy while fighting )....but had lots of 'bravery' and fought naked with lots of blue paint on their bodies to intimidate their enemies. (think of African 'Zulu" tribal warriors vs. the British in South Africa during 1800s...sending just 1000s into same area to be mowed down by British guns..they just kept coming. the roman military was as well trained , organized as the british military during 1800s, but without guns with gun powder , but I believe they did have 'gun" type of weapons that shot arrows)

If they had Ar-15s they wouldn't have had to rush anyone, Who knows why but i can say war is a series of bad decisions. You learn what not to do if you live to regret your mistakes.