Calling all armchair generals! Boudica's Last Stand.

[MonsGraupius]

That is what he did, and that is why the battle was fought in the vicinity of St Albans, and that is why St Albans is the only place Tacitus mentions besides Colchester and London.

Tacitus mentions St.Albans, because it was destroyed at the same time as London and was a more important place than London. Being more important, if Suetonius had gone to St.Albans, Tacitus would have said all he said about London but for St.Albans, because London would then be "just another place ransacked".

Suetonius goes south over the Thames. There is no doubt about that. However, what I should have included is the possibility that Suetonius, having regrouped at Calleva, or there may be a closer site, he could have chosen to cross his fortified wall of the Thames-Severn at London. This would be a repeat of Caesar's crossing of the Thames. It would be at the few sites between Chertsey and London Bridge.

At this point, Suetonius is back "at London" ... I was going to say "no change ... the same starting point if he just headed north without waiting". But this time has regrouped and resupplied and there is no army "up north" to draw him along Watling Street. This time he is moving from London forward to draw Boudica into battle and Watling Street looks a strange way to do that.

However, I had thought it would be the same. I now realise writing this that Suetonius, like Agricola, is going to want to take a coastal route so that he can be resupplied by boat. It seems the logical route is now to Colchester and up the coast to Norfolk. I'm not aware of any hills that could fit the "Ravine" topology with a coastal route to Norfolk.

WHY THE MAD DASH?
I am starting to understand why this ridiculous mad dash up Watling street was invented when it defies all logic. Between London and Norfolk the terrain is very flat. It's only to the NW of London that we get the hills which produce the Ravines necessary to fit the battle site description. So, people needed to find an excuse for Suetonius to head NW ... hence the narrative about Suetonius not being with his army and having to go back up Watling street to get to the Chilterns ... having accepted this ridiculous narrative ... we then get the standard: "why can't it be in this valley" texts, all of which enforce the stupidity of the first narrative of a dash down Watling street. The same thing happened to the battle of Mons Graupius ... every Tom Dick and Harry saw a hill, wondered if it was the battle site, and then set about distorting and shoehorning the facts to fit.