Calling all armchair generals! Boudica's Last Stand.

[Renatus]

All this action occurs in London!

Of course it does.  I don't know why you keep harping on about this; nobody has said anything different.  I repeat what Tacitus tells us.  The inhabitants of London who were overwhelmed by the rebels were those who could not leave because of sex or age or those who would not leave because of their attachment to the place.  None of them were going anywhere, bridge or no bridge, and you cannot use their fate to support your theory that Suetonius retreated south of the river.