Talk through the timeline and, as you do so, send in the Celts to live in Britain, then send in the Romans (in fighting formation) just to the edge of Britain. (Invite some Celts to mime fighting them.) As you continue through the oral timeline, "evict" the Romans, and then send them back again.
At the same time, nominate one of the Celtic girls as Queen Boudicca (the boys in my class were quite miffed that the warrior leader was female).
Send in Anglo-Saxons in ones and twos, either to fight or to trade. Make them come and go, as this mirrors what really happened. Gradually allow most of them to settle in Britain, but at the same time expel most (not all) of the Romans. Invite the Vikings to send warring parties. They can capture some children and take them away, and then some can return and settle in Britain.
I found the children loved all the miming drama of fighting and trading.
They really appreciated that Britain in this period was constantly changing, with differing groups coming and going - some fighting, some trading, some returning to their homeland and some staying and settling in Britain.
By making reference to Britain today children began to think about how this pattern of new groups coming and going, some staying and settling, is a feature of our history.
Cathy Walsh, deputy headteacher, Lutley Primary School, Dudley