Calling all armchair generals! Boudica's Last Stand.

[MonsGraupius]

I will give you my answer, but first ask yourself, Why would the residents of London Need to be fit and strong to keep up with SP if they were only going to cross the River Thames, to safety? And if not to safety, then the River is no longer the barrier you suggest. I cannot understand why their health would matter unless they had to travel a considerable distance at some speed. Please also note SP and the civilians met up with his available reinforcements after London and after St Albans were lost, which puts him at least 30 miles away.

Good question, and much appreciated (not a lot to read online just now). The section you refer to is this:

Those who were chained to the spot by the weakness of their sex, or the infirmity of age, or the attractions of the place, were cut off by the enemy

The phrase "cut off", means that they were left with no escape, which is something that only happens if they are totally surrounded, or if there is a barrier like the Thames where the few crossings are blocked.

The previous sentence refers to people ... presumably in London:

Nor did the tears and weeping of the people, as they implored his aid, deter him from giving the signal of departure and receiving into his army all who would go with him.

So, it might at first be presumed that the people "cut off" were in London. However, I would suggest that rather than being in London when they started, they started in settlements north of the Thames and were cut off when London was taken by Boudica. What is likely to have happened, is that they were making their way toward London bridge, and then discovered that London was taken or worse, Suetonius when fleeing had destroyed the bridge.

Unable to reach the crossings in time because of their "weakness of their sex, or the infirmity of age", they were then unable to cross the Thames, and totally cut off from the Romans on the other side.

They presumably went up the Thames trying to find somewhere else to cross. It's not that great a distance across the Thames, so, we can assume that they could call across. Indeed, if they had servants, they would have swum across the Thames to attempt to plead for help.

Presumably, those in good health, could, have moved quickly along the north bank ahead of Boudica to find a ford. Today the Thames is tidal to Teddington. In the Roman period it was probably tidal to around Richmond. There is suggestions there was a ford at Hampton court, but that may been lower downstream in the Roman period. But let's say there was one at Richmond, which is about 12miles from London.

We can imagine Boudica's hoard, having reached London and finding their way blocked, then decided to take revenge on all the Romans they could. As such they spread out overtaking the slowest of those attempting to flee along the north of the Thames, and presumably they were then slaughtered in view of the Romans, who could do nothing. That kind of thing would be reported.

How do you explain "cut off"
In fact, the problem with this passage is those who claim that Suetonius went North. Because how then does Boudica "cut off" those in London who, as you point out, can simply walk across London Bridge? And, it is not possible to "surround them" in London, because the Thames prevents them flanking London and coming from the south. The only way to be cut off in London, is if the crossings of the Thames had been destroyed by Suetonius, which means that Suetonius must be south of the Thames. If you suggest Suetonius went to St.Albans, then all he is doing by destroying the Thames crossings is to cut himself off from his own supplies which come via the SE from Gaul.

Please also note SP and the civilians met up with his available reinforcements after London and after St Albans were lost, which puts him at least 30 miles away.

What "Like ruin fell on the town of Verulamium" means, is that Suetonius never even attempted to help Verulamium. it likewise was "cut off" and surrounded by Boudica.

if Suetonius' army was split, then it met up to the south of the Thames.